President Donald Trump threatened Thursday to immediately double US tariffs on Mexico if the country does not stop a migrant caravan of more than 1,000 people heading north toward the United States.

“Here we go again!” Trump wrote on social media, warning that the migrants “will not be accepted” and demanding that Mexico stop the group. He said tariffs on Mexico would be “IMMEDIATELY DOUBLED” if the caravan is not halted.

An estimated 1,500 migrants, mostly from Central America, left the southern Mexican city of Tapachula near the Guatemalan border on Tuesday. The group, which includes many families, is hoping last week’s Democratic victory in the US midterm elections could lead to more favorable immigration policies and eventually allow them to live and work in the United States.

Mexican President Claudia Sheinbaum confirmed that a group was moving north but said no migrant caravans have reached the US border since Trump returned to office. She said migrants had been warned about the difficulty of entering the United States and that Mexico was seeking to return them to their countries of origin, while adding that there would be “no acts of repression.”

US Homeland Security Secretary Markwayne Mullin backed Trump’s warning, saying the administration would use “all assets” to secure the border and that the caravan would not be allowed to enter the United States.

The tariff threat comes as Washington and Mexico negotiate a new trade agreement. Trump declined in July to extend the US-Mexico-Canada trade pact, adding another point of tension between the two countries.

The confrontation also comes as Trump has recently acknowledged political backlash over his administration’s deportation policies. In a Sunday interview with CBS’s 60 Minutes, he said the deportation effort had been “too tough” and expressed openness to reaching an immigration agreement with Democrats once they take control of Congress in January.

This article was independently written by the BJL Newsroom based on reporting from Reuters.