President-elect Trump said he spoke with Mexican President Claudia Sheinbaum Pardo, saying she has agreed to "stop Migration through Mexico, and into the United States" following threats this week to significantly tariff goods from coming into the U.S. from its southern neighbor. 

Trump vowed to impose 25% tariffs on Mexico and Canada if both nations failed to do more to stop the flow of illegal immigrants and drugs into the U.S. Sheinbaum, who recently took office, said on Wednesday that Mexico would retaliate if Trump followed through on his promise. 

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"If there are U.S. tariffs, Mexico would also raise tariffs," she said during a press conference. 

On Wednesday, Trump said he spoke with his Sheinbaum about the matter. 

"Just had a wonderful conversation with the new President of Mexico, Claudia Sheinbaum Pardo," he wrote on Truth Social. "She has agreed to stop Migration through Mexico, and into the United States, effectively closing our Southern Border. We also talked about what can be done to stop the massive drug inflow into the United States, and also, U.S. consumption of these drugs. It was a very productive conversation!"

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In a subsequent post, he said that: "Mexico will stop people from going to our Southern Border, effective immediately. THIS WILL GO A LONG WAY TOWARD STOPPING THE ILLEGAL INVASION OF THE USA. Thank you!!!"

In a post on X, Sheinbaum said she spoke with Trump by phone and that the two discussed "strengthening collaboration on security issues" and that the conversation was "excellent," Reuters reported. 

Trump has long complained that Mexico has failed to do enough to stop the flow of migrants and illicit drugs on its side of the southern border.  

In a post on X, Sheinbaum said she explained the "comprehensive strategy" Mexico has employed to address the "the migration phenomenon, respecting human rights."

"Thanks to this, migrants and caravans are assisted before they reach the border," she wrote. "We reiterate that Mexico's position is not to close borders but to build bridges between governments and between peoples."

Trump also threatened to impose an additional 10% tariff on China over the massive amounts of fentanyl coming into the U.S. from Mexico. 

U.S. officials have frequently said that illicit fentanyl is manufactured in Mexico using Chinese precursors and then smuggled across the border by drug cartels.

Fentanyl, a synthetic opioid that is up to 50 times stronger than heroin and can be fatal in small doses, has claimed the lives of hundreds of thousands of Americans and is a factor in many drug overdose deaths. 

On Wednesday, Trump said he would be working on a large-scale ad campaign explaining the dangers of fentanyl. 

"Millions of lives being so needlessly destroyed. By the time the Campaign is over, everyone will know how really bad the horror of this Drug is," he said.

In response to the threat of more tariffs, the China Daily newspaper – which is run by the Chinese Communist Party – published an editorial Tuesday saying, "The excuse the president-elect has given to justify his threat of additional tariffs on imports from China is far-fetched," according to Reuters.

Fox News Digital's Greg Norman contributed to this report.