London (CNN) President Donald Trump reaffirmed his intentions Tuesday to impose tariffs on Mexico in a bid to pressure the country into stepping up its efforts to stop migrants from crossing into the United States.

With Republican lawmakers in Washington weighing steps to block the tariffs Trump has threatened to impose, the President sought to remove any doubt that he is prepared to make good on that threat, saying it is "more likely" he will impose the tariffs next week. At the same time, he also suggested that Mexico had already begun to take some steps to stem migrant flows and said he believes the country will "step up."

"We're going to see if we can do something. But 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," Trump said during a news conference in London, where he took questions alongside British Prime Minister Theresa May

"Mexico shouldn't allow millions of people to try and enter our country. And they could stop it very quickly and I think they will, but if they won't, we're going to put tariffs on them," Trump said. "I think Mexico will step up and do what should've been done."

Trump's comments came as Republican lawmakers grappled with Trump's threat. Several members are eyeing legislative options to push back on the tariffs and White House officials are slated to attend the Senate Republicans weekly closed-door policy lunch to make the case for the President's plans.

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