The U.S. is considering delaying President Donald Trump’s threatened tariffs on Mexico as talks continue over stemming the flow of undocumented migrants and illegal drugs from Central America, according to people familiar with the matter.

Mexico is pushing for more time to negotiate over concerns the two sides won’t be able to reach agreement on all the steps Mexico would have to take to avert the tariffs, one person said. Trump has said the tariffs will be enacted on Monday.

One U.S. official said the most likely outcome is still that a 5% tariff goes into effect. But the official said U.S. negotiators recognize that Mexico is taking the talks seriously and working quickly to address Trump’s concerns. If the 5% tariff is triggered but Mexico follows through on promises to crack down on migration, the duties could be short-lived, the official said.

U.S. stock indexes jumped to session highs on the news, while Mexico’s peso strengthened against the dollar.

Trump is traveling in Europe this week. Vice President Mike Pence and Secretary of State Michael Pompeo took part in discussions with Mexican Foreign Minister Marcelo Ebrard on Wednesday, but neither was present at meetings today.

Ebrard said earlier today that there were unspecified “advances” after meeting with officials at the State Department.

No deal is expected out of a White House meeting today that was set to begin at 2 p.m., an administration official said. The meeting is staff-level only for the U.S., without any cabinet secretaries, Pence or Trump in the room.

The White House didn’t immediately respond to a request for comment.

While Trump said progress was made during Wednesday’s 90-minute meeting and that “something pretty dramatic could happen” in the coming days, he continued to hold out the threat that the U.S. will follow through with tariffs.

Mexico’s proposal to delay the implementation matches comments by top Republican lawmakers. Senate Majority Leader Mitch McConnell told administration officials that Trump should hold off on imposing tariffs on Mexico until the president can personally make his argument to Republicans in Congress, according to people briefed on the conversation.

“We’ve told Mexico the tariffs go on” if no deal is made, Trump told reporters in France, where he spoke at a commemoration of the 75th anniversary of D-Day. “They have to step up to the plate.”

“If no agreement is reached, Tariffs at the 5% level will begin on Monday, with monthly increases as per schedule,” Trump tweeted Wednesday. “The higher the Tariffs go, the higher the number of companies that will move back to the USA!”

Trump last month announced a 5% tariff on all imports from Mexico unless the country takes “decisive measures” — as judged by his administration — to stem migrants entering the U.S. He said the tariffs would begin June 10 and scale up incrementally until they reach 25% on Oct. 1. Mexico is the second largest source of U.S. imports after China.