“I don’t think they’ll do that,” the president said of Republicans in Congress potentially voting to stop the tariffs. “I think if they do, it's foolish. There is nothing more important than borders.”
Last week, Trump threatened to slap a 5 percent tariff on Mexico until the illegal immigration surge at the southern border is "remedied."
During a Tuesday press conference in London with outgoing Prime Minister Theresa May, the president said he wants to “see security at our border” and predicted that the tariffs “will take effect next week.”
He said his administration will meet with Mexican officials to try to come to a solution but added, “I think it's more likely the tariffs go on.”
The president called on Mexico to “step up and give us security for our nation,” adding that “millions and millions of people are coming right through Mexico.”
But Mexico said earlier Tuesday that an agreement was likely to avoid the threatened 5 percent tariff on Mexican imports.
"By what we have seen so far, we will be able to reach an agreement," Mexican Foreign Minister Marcelo Ebrard said during a news conference at Mexico's Embassy in Washington. "That is why I think the imposition of tariffs can be avoided."
Ebrard said his team will be prepared for a non-agreement scenario despite his optimism that a deal will be reached.
Ebrard arrived in Washington over the weekend to meet Wednesday with Secretary of State Mike Pompeo. Mexico calls the potential tariff hurtful to the economies of both countries and useless to slow the northbound flow of Central American migrants.
Some Republican lawmakers warn that tariffs on Mexican imports will hit U.S. consumers, harm the economy and jeopardize the new United States-Mexico-Canada Agreement trade pact that the White House wants Congress to approve this year.
"We need to put our heads together and try to come up with a solution," Texas Republican Sen. John Cornyn warned Monday.
The Associated Press contributed to this report.