President Donald Trump said that he would impose a 5% tariff on Mexican goods until that country stops immigrants from entering the U.S. illegally.

The tariff would take effect on June 10 “until such time as illegal migrants coming through Mexico, and into our country, STOP,” Trump said in a Twitter post on Thursday night.

He warned that the levy “would gradually increase until the illegal immigration problem is remedied at which time the tariff will be removed.”

The tariffs could rise as high as 25% on Oct. 1, Trump said in a statement released by the White House.

“Mexico must step up and help solve this problem,” Trump said in the statement.

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