Central American migrants eager to beat a crackdown by Mexico on its southern border with Guatemala scrambled into the country on Thursday as the government prepared to send thousands of National Guard members to plug gaps in the porous frontier.

Mexico has agreed with the United States to demonstrate by late July that it can contain a surge in U.S.-bound migrants, following a threat from U.S. President Donald Trump to impose tariffs on Mexican goods if it failed to do so.

Foreign Minister Marcelo Ebrard said this week that Mexico would beef up control of its southern border, including sending 6,000 members of the National Guard. The deployment was due to begin on Wednesday though witnesses saw no signs of the deployment.