President Trump on Thursday said talks with Mexico are progressing but warned that he’s ready to roll out tariffs on Mexican imports even as Republicans threatened to block them in Congress.

“We’re having a great talk with Mexico. We’ll see what happens. But something pretty dramatic could happen,” Trump told reporters in Ireland before heading to Normandy for commemorations marking the 75th anniversary of D-Day. “We’ve told Mexico the tariffs go on. And I mean it, too. And I’m very happy with it.”

Mexican officials have been meeting with their American counterparts in Washington, DC, this week to find a remedy before the first of the tariffs take effect on Monday.

In a tweet sent overnight from Ireland, Trump said the negotiations will resume on Thursday but cautioned that “if no agreement is reached, Tariffs at the 5% level will begin on Monday, with monthly increases as per schedule.”

Under Trump’s plan, the tariffs would increase by 5 percent increments until they reach 25 percent in October unless Mexico stems the flow of illegal immigrants from Central American countries passing through Mexico on their way to the US border.

The president said the solution is up to Mexico.

“They have to step up, and they have to step up to the plate, and perhaps they will. We’re going to see. They can solve the problem,” he said.

Mexican Foreign Secretary Marcelo Ebrard, who met with Secretary of State Mike Pompeo and Vice President Mike Pence, said immigration was the focus of the talks rather than the tariffs and expressed optimism that they could reach a breakthrough.

But Republicans, worried that the tariffs would have harmful effects on the US economy and scuttle the USMCA trade deal with Mexico and Canada, have threatened to block the duties.

Trump slammed Congress, especially Democrats, for opposing his tariff plan.

A “lot of people, senators included, they have no idea what they’re talking about when it comes to tariffs,” he said. “They have no — absolutely no idea.”

He said the US has the upper hand in negotiations with Mexico.

“When you have the money, when you have the product, when you have the thing that everybody wants, you’re in a position to do very well with tariffs, and that’s where we are,” Trump said. “We’re the piggy bank.”

The talks are playing out as Customs and Border Protection data shows the number of migrants crossing the border skyrocketed in May to more than 144,000 — a 32 percent increase over April.