President Donald Trump reaffirmed his intentions on Tuesday (4 June) 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, reported.

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, CNN reported.

He also suggested 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, according to CNN.

"I think Mexico will step up and do what should've been done."

CNN noted Trump's comments came as Republican lawmakers grappled with the 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.

Key Republican senators have slammed the president's proposed tariffs, which even several of Trump's top advisers privately oppose. For his part, Trump said it would be "foolish" for Republican lawmakers to take action to block the tariffs.

"I don't think they will do that, I think if they do, it's foolish," he said, before touting his high approval rating among Republicans.

US secretary of state Mike Pompeo is slated to meet Wednesday in Washington with Mexico's foreign minister to discuss the tariffs and the immigration issue, CNN added

The first tier of tariffs – at 5% – are set to go into effect on Monday barring a resolution between the US and Mexico. Trump has said the tariffs will ratchet up until they reach 25% on all imports from Mexico, a move that would likely harm both the US and Mexican economies, CNN said.

Earlier report: US plans new 5%+ tariffs on all Mexican imports