The United States pushed Mexico on Thursday to do more to curb the surge of Central American migrants headed north to the U.S., with President Donald Trump renewing his threat to impose a 5% tariff on imported goods from Mexico next week if no agreement is reached.

U.S. Vice President Mike Pence said that initial talks with Mexico this week were positive but that the U.S. wants Mexico to increase its efforts to curb the flow of thousands of migrants from Guatemala, Honduras and El Salvador looking for a better life in the U.S. and an escape from poverty and violence in their homelands.

'We welcomed the efforts of the Mexican officials to offer solutions to the crisis at our southern border, but we need Mexico to do more,' Pence said.

Trump, in Europe for D-Day commemorative events, tweeted that the latest talks were being held 'with the understanding that, if no agreement is reached, Tariffs at the 5% level will begin on Monday, with monthly increases as per schedule' that could push the taxes to 25 percent on an array of products by October.

Mexican Foreign Minister Marcelo Ebrard held meetings with U.S. officials at the State Department, while other negotiators from both countries met at the White House.

'We're not done yet,' Ebrard said. 'I think we are advancing.'

Mexico-Guatemala border patrols

The officials are discussing a deal calling for Mexico to sharply increase patrols of its border with Guatemala to curb migration, The Washington Post reported, with the deployment of 6,000 National Guard troops. The newspaper said Mexico and the U.S. could overhaul asylum rules throughout the region, requiring Central Americans to first seek refuge in Mexico rather than traveling through it to reach the U.S.

With such a plan in place, the United States could send Guatemala asylum-seekers to Mexico, and those from Honduras and El Salvador to Guatemala.

Late Wednesday, Trump tweeted, 'Progress is being made, but not nearly enough! The higher the Tariffs go, the higher the number of companies that will move back to the USA!'

He added Thursday in comments to reporters, 'We've told Mexico the tariffs go on, and I mean it, too.'

As Wednesday's talks ended, Ebrard said, 'What we want to avoid is the impact of the tariffs for the two economies, for the consumers, for the people of both countries.'

In Mexico City, President Andres Manuel Lopez Obrador reiterated his own optimistic position.

'We think that a deal will be reached,' he said, because it's important for Mexico and the United States to maintain healthy relations. It's vital 'that there be communication and an understanding. The best thing is free trade,' he added.

U.S. authorities say more than 100,000 undocumented migrants, mostly from the three Central American countries, have crossed into the United States in recent months. The U.S. government announced Wednesday that in May 144,000 migrants were detained at the border, up 32% from April. It was the highest monthly figure in 13 years.

Some Republican opposition

Some Republican lawmakers, normally close political allies of Trump, have said they will try to block the tariffs with legislation, which also would draw wide support from opposition Democrats. Numerous lawmakers fear rising consumer costs for Americans if the tariffs are imposed on Mexican goods, including cars and numerous food products exported to the U.S.

Trump said Republicans would be 'foolish' to try to stop him from imposing the tariffs.

In his comments Thursday, Trump also revisited his criticism of congressional Democrats for what he said was their refusal to 'fix the immigration laws.'