Mexico and the United States may explore additional steps in July to restrict illegal immigration from Central America, with the threat of tariffs hanging over Mexico if it does not do enough to satisfy US demands, officials said on Monday.

Mexican Foreign Minister Marcelo Ebrard said Brazil, Panama and Guatemala may need to be brought in to help if a deal unveiled last week between Washington and Mexico fails to reduce the number of US-bound migrants crossing Mexico.

The deal struck on Friday averted import tariffs on all Mexican goods, which US President Donald Trump had vowed to impose unless Mexico did more to curb migration.

The Trump administration said on Monday it could still apply tariffs if it judged that Mexico had not done enough, with US Secretary of State Mike Pompeo telling reporters it expected to see results within four to six weeks.

The deal cut between the two nations last week means Mexico will expand a program under which migrants applying for asylum in the United States wait out the process in Mexico.

Mexico also pledged to reinforce its southern border with Guatemala with 6000 members of its National Guard militarized police.

A major sticking point in last week’s talks was a US demand that Mexico be declared a “safe third country” for asylum seekers, requiring them to seek refuge in Mexico if they passed through the country on the way to the United States.