As Congress continues to feud over construction of a border wall, another Central American caravan of 10,000-plus migrants has entered Mexico and intends to reach the U.S.

The caravan, which first departed Honduras on Jan. 15, began as a smaller group of around 500 people. However, the caravan ballooned in size as it continued to travel across Central America. Numerous foreign nationals from Guatemala and El Salvador, eager over the possibility to apply for humanitarian visas in Mexico, joined along the way.

President Donald Trump made note of the caravan as it set course for the U.S., and derided Central American governments for doing “nothing” to stop it.

“A big new Caravan is heading up to our Southern Border from Honduras. Tell Nancy and Chuck that a drone flying around will not stop them. Only a Wall will work,” the president tweeted on Jan. 15.

“Mexico is doing NOTHING to stop the Caravan which is now fully formed and heading to the United States,” he tweeted again on Saturday. “We stopped the last two – many are still in Mexico but can’t get through our Wall, but it takes a lot of Border Agents if there is no Wall. Not easy!”

Many of the migrants are attracted by a new policy recently enacted by Mexican President Andrés Manuel López Obrador. The new left-wing president, who has criticized Mexico’s past treatment of migrants, is allowing many of them to apply for humanitarian visas, allowing them stay in the country legally as they try to gain access into the U.S.

Historically, migrants would reach the border and apply for asylum within the U.S., allowing them to disappear into the country without ever appearing to their immigration court date. The Trump administration has worked to prevent this by pressuring the Mexican government to keep migrants their country as they wait for their asylum cases to work through the U.S. courts — a policy known as “remain in Mexico.”

Mexico’s National Immigration Institute reported that it had processed a total of 10,343 migrants. About 75 percent were from Honduras, with the remainder coming from El Salvador, Guatemala, and a small number of Haitians, Nicaraguans Cubans and Brazilians.

The looming caravan, which further highlights the issue of immigration, comes as lawmakers in Congress continue to fight over border security. A bill that would have provided $5.7 billion in funding or a border wall failed a Senate floor vote on Thursday — as did a Democratic-backed bill that excluded wall funding.

The budget impasse has resulted in the longest partial government shutdown in U.S. history.