President Donald Trump said Mexico has “absolute power” to stop a caravan of Central American refugees from entering their country, a day after he threatened to pull out of the North American Free Trade Agreement over the flow of people and drugs into the U.S.

“Mexico has the absolute power not to let these large ‘Caravans’ of people enter their country,” Trump said in a Twitter posting on Monday. “They must stop them at their Northern Border, which they can do because their border laws work, not allow them to pass through into our country, which has no effective border laws.”

BuzzFeed has reported that a “caravan” of Central American immigrants led by Pueblos Sin Fronteras, or People Without Borders, has been making its way north in a march toward the U.S. border to seek asylum.

Trump on Monday also declared as “dead” an effort to strike a deal to assist immigrants brought to the country illegally as minors, and repeated a call for Senate Republicans to go to a simple 51-vote majority as a way to pass legislation more easily. Under the Deferred Action for Childhood Arrivals program, those eligible for protected status must have lived continuously in the U.S. since 2007 and entered the country before their 16th birthday, but Trump rescinded the program in September and gave Congress until March to strike a compromise.

“DACA is dead because the Democrats didn’t care or act, and now everyone wants to get onto the DACA bandwagon,” Trump said on Twitter. “No longer works. Must build Wall and secure our borders with proper Border legislation. Democrats want No Borders, hence drugs and crime!”

Lawmakers have been unable to strike a bargain, with the White House insisting any deal also include new restrictions on legal immigration as well as funding for the president’s border wall. Democrats rejected an offer as part of an omnibus spending package that would have given the president funding for his wall in exchange for a short-term extension of the program. A federal judge in January issued an injunction order keeping the program in place as courts consider legal challenges to the president’s bid to end DACA.