President Donald Trump slapped new tariffs on Mexico Thursday over its failure to stop illegal immigration to the U.S.

Trump said he would impose a five percent tax starting June 10 on all Mexican imports and increase the tax on a monthly basis “until such time as illegal migrants coming through Mexico, and into our country, STOP,” said Trump on Twitter.

In a statement released by the White House, Trump said, “Mexico must step up and help solve this problem.” The tariffs could go as high as 25 percent by October, according to the released statement.

The president’s comments caused a drop in several stock markets worldwide and sent the value of the Mexican peso tumbling. It also caused significant drops in market value for U.S car manufactures, which rely heavily on Mexican factories.

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Several prominent Republican lawmakers also criticized Trump for his decision, saying this move would hurt the U.S. economy and that immigration and matters regarding international economic relations should be dealt as separate issues.

“I think it was a mistake,” Sen. John Kennedy (R-Louisiana) said in an interview with Talking Points Memo on Sunday, adding: “I don’t think the President is going to impose these tariffs… He’s been known to play with fire, but not live hand grenades. And if he slaps a 25% tariff on Mexico, it’s going to tank the American economy. I think the President knows that.”

Trump has long railed against undocumented immigrants coming through the southern border, and his administration has painted them as criminals who bring drugs and diseases into the U.S.