LONDON — President Trump on Tuesday said he plans to move forward with imposing tariffs on Mexican imports next week as part of his effort to stem the flow of migrants crossing the southern border, and he called Republican senators “foolish” if they try to stop him.
Mr. Trump made the remarks at a news conference with Theresa May, the outgoing British prime minister.
“I think it’s more likely that the tariffs go on, and we’ll probably be talking during the time that the tariffs are on, and they’re going to be paid,” Mr. Trump said. When asked about Senate Republicans discussing ways to block the tariffs, Mr. Trump said, “I don’t think they will do that.”
He said, “I think if they do, it’s foolish.”
Mr. Trump’s latest threat — five percent tariffs on all goods imported from Mexico, rising to as high as 25 percent until the Mexican government stems the flow of migrants — has riled Republican senators who fear its impact on the economy and their home states.
But any vote to disapprove the tariffs would almost certainly face a presidential veto, meaning that both the House and Senate would have to muster two-thirds majorities to beat Mr. Trump. Opponents would use the same motion of disapproval that they tried to use to block the president from grabbing federal money for a border wall that was not appropriated for that purpose. That motion did pass Congress with significant Republican support, but not enough to overcome Mr. Trump’s veto.
And with significant numbers of Republicans backing Mr. Trump’s hard line on immigration, there is little reason to believe opponents of the tariffs could overcome a veto this time.
Senator John Thune of South Dakota, the No. 2 Senate Republican, said on Monday that his colleagues were clearly uneasy with Mr. Trump’s tariff threat. Senators, he said, need to hear from administration officials directly on the “rationale for what they are doing” and on what authority they are imposing the tariffs. He said he hoped the White House would be willing to reach an agreement with Mexico to delay the tariffs “and hopefully find better ways of solving the immigration issues.”
Asked if the Senate could end up voting to try to block this, he said, “My guess is at some point if they continue down this path and they escalated the tariff, Congress is going to want to be heard from for sure.”
“I think the broader economic considerations need to be carefully considered when they are moving forward with any kind of new policy like this, something that is from our standpoint completely new and unheard-of,” he said.
Senator Charles E. Grassley, Republican of Iowa and the Finance Committee chairman, said on Monday he would hold his fire until after a meeting on Wednesday between Secretary of State Mike Pompeo and Mexican officials. Mexico’s foreign minister is leading a delegation to Washington this week to try to defuse the situation with the Trump administration. And while Mexican officials have taken steps to crack down on illegal immigration, they have also warned that they could respond with retaliatory measures of their own.
Mr. Grassley added, “I intend to continue saying the same things I’ve been saying” in opposition to the use of tariffs to affect immigration policy.
But Mr. Trump has supporters, and Republicans have been loath to oppose him on immigration. Senator Marco Rubio of Florida, once a moderate on immigration policy, took to Twitter to say he was within his rights to use tariffs to force Mexico’s hand.
Representative Hakeem Jeffries of New York, the chairman of the House Democratic Caucus, told reporters on Tuesday that House Democrats still “want to get to yes” on passing Mr. Trump’s new trade deal with Canada and Mexico, an updated North American Free Trade Agreement that could be torpedoed by new tariffs on Mexico. But he declined to forecast whether the House would try to block the tariffs that could stand in the way.
“The problem that we confront in this country is that the president often conducts himself in an erratic fashion as it relates to economic policy, particularly in terms of his deployment of tariffs,” Mr. Jeffries said.
He added: “The administration’s tariff policy is erratic and all over the place. We will see what the Senate Republicans ultimately decide to do, but we will certainly strongly consider proceeding in a way that is appropriate and consistent with our legislative powers.”
Mr. Trump seemed unimpressed when a reporter noted that Mexican officials say that they’ve increased the number of migrants they’ve apprehended coming into their country from elsewhere in Central America. He offered no specifics on what it would take to keep the tariffs from being imposed.
“Look, millions of people are flowing through Mexico,” Mr. Trump said. “That’s unacceptable.”