Sen. Ed Markey, D-Mass., claimed that people should be terrified that President-elect Trump will possess the power to initiate a nuclear attack. 

In a post on X, Markey noted, "Come January, Donald Trump will have the sole authority to launch a nuclear strike. This should terrify you. That's why @RepTedLieu and I are urging @POTUS to put guardrails on presidential authority to start nuclear war."

Trump — who trounced Vice President Kamala Harris in the 2024 White House contest by winning both the Electoral College and the popular vote — previously served as president from early 2017 through early 2021. And during his Oval Office tenure, he never used nuclear weapons.

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He has also been outspoken about the massive danger posed by nuclear weapons.

"To me, we have one really major threat: That's called nuclear weapons," Trump said earlier this year. "This isn't Army tanks going back and forth and shooting at each other. This is obliteration," he said of the powerful weapons. "We have incredible stuff, so does Russia. China has much less but" will "catch up," Trump said, calling the issue the "single biggest threat by far to civilization."

Josh Barnett, who lost in a Republican primary for an Arizona state Senate seat earlier this year, responded to Markey's post by writing, "LOL he had the authority the last four years he was in office." 

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Others made the point as well.

"Hey buddy, he was already president once," Tom Gillis, who describes himself on X as a "Former PGA tour player," declared in response to the lawmaker's post.

"He had the power before and didn’t use it," another individual, Shonathan Perrius, tweeted.

In a letter to President Biden, Markey and Rep. Ted Lieu, D-Calif., declared that during his waning time in office, the commander-in-chief could "safeguard the system against Donald Trump or any future unstable president, and make it constitutional."

"We urge you to announce that henceforth it will be the policy of the United States that it will not initiate a nuclear first strike without express authorization from Congress. In a situation where the United States has already been attacked with nuclear weapons, the president would retain the option to respond unilaterally," the two Democrats declared in their letter to the president.

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The lawmakers have long advocated for the policy shift, repeatedly pushing legislation on the issue.

"As the coauthors of the Restricting First Use of Nuclear Weapons Act — proposed legislation that prohibits any U.S. president from launching a nuclear first strike without prior congressional authorization — we urge you, in your remaining time in office, to change this unconstitutional policy," they said in their letter to Biden.

"We first introduced this act during the Obama administration not as a partisan effort, but to make the larger point that current U.S. policy, which gives the president sole authority to launch nuclear weapons without any input from Congress, is dangerous. As Donald Trump prepares to return to the Oval Office, it is more important than ever to take the power to start a nuclear war out of the hands of a single individual and ensure that Congress’s constitutional role is respected and fulfilled," Markey and Lieu noted.

President-elect Trump will take office just as Iran has the potential to become the world’s 10th nuclear-armed state, and it’s unclear if either side knows how it will approach the other. 

Judging by Trump’s last time in office, it would suggest he would come out the gate with a combative tone — having instituted a "maximum pressure" campaign to "bankrupt" the regime. His secretary of state pick, Sen. Marco Rubio, R-Fla., has been an unyielding Iran hawk in the Senate. 

After the regime fired 200 missiles toward Tel Aviv last month, Rubio said: "Only threatening the survival of the regime through maximum pressure and direct and disproportionate measures has a chance to influence and alter their criminal activities."

That could reinstate — and eliminate — any waivers for oil sanctions. It could mean threatening not to conduct business with countries that buy Iranian fuel products. 

Rep. Michael Waltz, R-Fla., Trump’s pick for national security adviser, is of a similar mind. 

Last month, when the Biden administration urged Israel to keep its counterstrikes "proportional," Waltz slammed President Biden for pressuring Israel "once again to do less than it should." 

He suggested Israel strike oil facilities on Kharg Island and Iran’s nuclear plants in Natanz, a move the Biden team feared Iran would deem escalatory. 

Last month, Trump appeared to rule out the U.S. getting involved in any effort to take out Iranian Supreme Leader Ayatollah Khameini and his government. "We can’t get totally involved in all that. We can’t run ourselves, let’s face it," he said.

"I would like to see Iran be very successful. The only thing is, they can't have a nuclear weapon."

Trump has said he does not want Iran to have nuclear weapons, but has not laid out how he would stop it from doing so. 

"I'm not looking to be bad to Iran, we're going to be friendly, I hope, with Iran, maybe, but maybe not. But we're going to be friendly, I hope, we're going to be friendly, but they can't have a nuclear weapon," he said at a New Jersey press conference in August. 

Last month, Trump suggested Israel strike Iran’s nuclear facilities. 

Following the Iranian missile attacks, he suggested Israel should "hit the nuclear first and worry about the rest later." 

On Thursday, Iran said it was activating "advanced" centrifuges after the International Atomic Energy Agency (IAEA) board of governors censured it for failing to cooperate with the U.N. nuclear watchdog. Without cooperation, the world is in the dark about how quickly Iran is advancing its technological capabilities to use its uranium fuel for a bomb. 

"We will significantly increase enrichment capacity," Behrouz Kamalvandi, Iran's atomic energy organization spokesman, said after the censure. 

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What’s standing between Iran and a fully formed nuclear weapon is both a political and a technological question. 

While the nation has enough fissile material for a nuclear weapon, the process of turning that into a warhead could take anywhere from six to 12 months, according to Nicole Grajewski, nuclear policy expert at the Carnegie Endowment for International Peace. 

"That’s when Iran would be most vulnerable to attack," she said. "Iran could probably make a dirty bomb from its current stockpile." 

Over the years, Iran’s nuclear progress has been set back by international sanctions, COVID-19, high-profile assassinations of its nuclear scientists and attacks and sabotage on its nuclear facilities led by Israel’s intelligence agency Mossad. 

And announcing they have a nuclear weapon could threaten Iran’s longtime goal of regional hegemony. 

"Iran is less isolated than it was four years ago, but it’s still pretty isolated. Announcing they are nuclear would trigger an arms race in the Middle East," predicted Simone Leeden, former Deputy Assistant Secretary of Defense for the Middle East. 

"Saudi Arabia and the UAE would decide they will pursue nuclear weapons the minute Iran declares it has its own. Another action they could and would take is deepening ties with Israel." 

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Iran also understands that producing a nuclear bomb would likely evoke a military response from Israel and the U.S. under Trump. 

After years of trying to assassinate Trump, the Iranians don’t seem to have figured out whether to approach the U.S. relationship under Trump with a combative or diplomatic tone. Just last month, they told President Biden they would not make any efforts to kill the president-elect going forward. 

"I think that there's been a lot of mixed signaling from the kind of Trump transition team is, you know, you see Brian Hook being appointed, who was behind this maximum pressure and sanctions," said Grajewski. But then, on the other hand, Trump envoy Elon Musk reportedly met with Iranian officials to discuss how the two nations could dial back tensions. 

"I think that he is being opaque on purpose," said Leeden. "I don't think he wants to show his cards as a negotiator." 

"In all likelihood, maximum pressure is going to be restored," said Behnam Taleblu, Iran expert at the Foundation for Defense of Democracies. "U.S. partners are asking now, to what end? Is it towards regime collapse? Is it towards a deal? What if the Iranians don't negotiate in good faith?"

Former Israeli officials have suggested Prime Minister Benjamin Netanyahu might be emboldened to strike Iranian nuclear facilities with the go-ahead from the Trump administration. But a lot of Iran’s centrifuge and enrichment facilities are deep underground, complicating a bombing campaign against them.

To get to them, Israel would need the U.S.' Massive Ordnance Penetrators (MOP), or "bunkbuster bombs." 

"It would require U.S. involvement — either the direct transfer of this, which is currently not really discussed — that would be pretty escalatory — or Israel getting the United States to also conduct this mission," said Grajewski. 

The Trump team will also place a high priority on bringing Saudi Arabia into the Abraham Accords, solidifying the Sunni Muslim alliance against Iran. But the Saudis have insisted the U.S. and Israel must recognize a Palestinian state for such a deal to get done. 

"The incoming administration wants to quiet down this kinetic energy in the Middle East quickly, because we have bigger fish to fry as a country," said Leeden.

The U.S. has long looked to pivot its military focus away from the Middle East and toward the Indo-Pacific. The outbreak of war between Israel and Hamas after Oct. 7 tore that focus back to the Arab world. 

Iran has increased its nearly weapons-grade uranium, a United Nations watchdog found, defying international demands to rein in its nuclear program.

Iran now has enough uranium at 60% purity, just below the 90% purity needed for a weapon, to produce about four nuclear bombs, an International Atomic Energy Agency (IAEA) report said. 

The report found Iran had about 400 pounds of uranium enriched to 60% as of Oct. 26, up 40 pounds from August. 

Around 92 pounds of uranium, enriched at 90%, is needed to make an atomic weapon. 

Iran’s overall stockpile of uranium enriched at any level reached about 14,560 pounds, up 1,880 pounds from August.

It comes as Iran has offered to cease enriching uranium beyond 60% – but only if the European Union and the United Kingdom cease their efforts to slap new sanctions on Iran and the IAEA drops a censure resolution it is pursuing.

During a meeting between IAEA general director Rafael Grossi and high-level Iranian diplomats, "the possibility of Iran not further expanding its stockpile of uranium enriched up to 60% U-235 was discussed, including technical verification measures necessary for the Agency to confirm this, if implemented," Grossi said. 

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He added that Iran said it would consider accepting agency inspectors to conduct oversight of its nuclear materials. 

Experts say there is no credible use of 60% uranium at the civilian level. 

Concerns have swelled among Western nations that Iran could decide pursuing a nuclear bomb is its best deterrent, after Israel hollowed out Hamas and Hezbollah, Iran’s biggest proxies. U.S. intelligence suggests they've improved their manufacturing capabilities for doing so over the past year. 

It's not yet clear whether President-elect Trump will come in with a combative or diplomatic tone toward Iran, but he's promised to crack down on sanctions on the regime that he claims President Biden failed to enforce. 

The European Union on Monday widened sanctions against Iran for its alleged support for Russia in the war in Ukraine, including targeting the national seafaring company and ships used to transfer drones and missiles. Acting in tandem, the U.K. froze the assets of the Islamic Republic of Iran Shipping Line.

Foreign Minister Abbas Araghchi denied that Iran was aiding Russia and warned the sanctions would prompt Iran to retaliate. 

"There is no legal, logical or moral basis for such behavior. If anything, it will only compel what it ostensibly seeks to prevent," Araghchi wrote on X.

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"Freedom of navigation is a basic principle of the law of the sea. When selectively applied by some, such shortsightedness usually tends to boomerang," Araghchi wrote.

The IAEA board is expected to move forward with a European-backed censure resolution, which could lead to the issue being escalated to the U.N. Security Council for possible measures against Tehran. 

That resolution would condemn Tehran's lack of responsiveness and call for creating a comprehensive report of all open questions about Iran's nuclear work. 

Iran has not formally decided whether to build a nuclear bomb, according to the latest available U.S. intelligence. But as of September 2024, Iran could produce weapons-grade uranium in about seven days and have enough for six to nine nuclear bombs within a month if it wanted to, according to David Albright at the Institute for Science and International Security.