President Donald Trump during a bilateral meeting with Taoiseach Leo Varadkar at Shannon airport on June 5, 2019 in Shannon, Ireland. President Trump will use his Trump International golf resort in nearby Doonbeg as a base for his three day stay in Ireland. The resort employs over 300 local people in the area and the village will roll out a warm welcome for the 45th President of the United States.

In past years, the undocumented migrants who crossed the U.S.-Mexican border were mostly Mexicans, but increasingly they are Central Americans who are passing through Mexico to get to the United States.

"We have explained that there are 6,000 men and that they will be deployed there," Mexico's Foreign Minister Marcelo Ebrard told reporters after meeting with U.S. negotiators, according to the news agency.

The move comes as Mexico tries to hash out a deal with the Trump administration to avoid new tariffs.

Mexico will send its national guard to its border with Guatemala to stem the flow of undocumented migrants who are entering Mexico on the way to the U.S., Reuters reported Thursday.

Talks between U.S. and Mexican officials that ran through Wednesday and Thursday are set to recommence on Friday.

If the two countries can't work out an agreement by Monday, President Donald Trump said he will slap 5% tariffs on all goods imported from Mexico.

A White House official told NBC News that "significant progress is being made on the talks."

Mexican Ambassador to the United States Martha Barcena told CNBC on Thursday that negotiators had "a very good discussion, a very good debate."

She said that the Mexican delegation "explained to [the U.S.] all the enforcement measures that Mexico is taking" to address immigration issues.

But the talks aren't over yet, Barcena said: "We are still talking about all the legal aspects of the cooperation that we are having on migration."

Trump, who on Thursday was in Normandy, France, to commemorate the 75th anniversary of the D-Day invasion during World War II, doubled down on his tariff threat before the second round of talks began.

"We've told Mexico, 'the tariffs go on,' and I mean it too. I'm very happy with it," Trump told reporters.

While Trump wants to get a deal with Mexico wrapped up soon, the likeliest scenario is that the two countries will strike an agreement between June 10 and July 1 — the date when Trump's tariffs on Mexican goods ratchet up to 10%, a senior administration official told CNBC.

Trump has threatened to raise the tariffs as high as 25% by October if Mexico doesn't take "effective actions" to stem the flow of undocumented migrants to the southern U.S. border.

WATCH: White House says still moving forward with Mexico tariffs