US President Donald Trump’s administration plans to send about 5,200 troops to the southern border with Mexico by the end of this week, escalating his response to a caravan of migrants heading toward the U.S. just days before the midterm elections.

The move comes as the administration considers additional executive action designed to block refugees from entering the country. The administration previously planned to deploy about 800 additional troops to the U.S.-Mexico border.

General Terrence O’Shaughnessy, head of United States Northern Command, announced the deployment in a news conference on Monday. In addition to supporting the border patrol with logistical and medical help, he said the military will also provide resources ranging from Blackhawk helicopters and drones to 22 miles of barbed wire.

Trump has made illegal immigration a front-burner issue in the weeks before the midterm congressional elections on Nov. 6, believing the issue motivates his supporters to turn out to vote and creates political headaches for Democrats. As part of that effort, the president has amplified concerns about the migrant caravan, which largely consists of individuals from Honduras, El Salvador and Guatemala.

Customs and Border Patrol Commissioner Kevin McAleenan, speaking at the same event, said U.S. authorities are tracking the caravan of refugees, currently estimated at around 3,500 people, as well as another group between Guatemala and Mexico of about 3,000 people.

“We will not allow a large group to enter the United States in an unsafe and unlawful manner,” McAleenan said.

Trump earlier Monday tweeted that “very bad people” were among the migrants seeking asylum.

“Many Gang Members and some very bad people are mixed into the Caravan heading to our Southern Border. Please go back, you will not be admitted into the United States unless you go through the legal process. This is an invasion of our Country and our Military is waiting for you!” Trump tweeted.

Trump has suggested without evidence that Democrats could be behind funding the caravan. Vice President Mike Pence has said he believes the migrants were organized by the Venezuelan government and unnamed leftist groups.

The White House is considering unveiling an executive action this week that would seek to block the entry of refugee-seeking migrants at the southern border by using the same authority Trump employed in his earlier ban prohibiting travel from certain Middle Eastern countries, the people said. The announcement – which Trump was considering announcing as soon as Tuesday – would effectively bar those seeking asylum from entering the country.

A White House official said the president hadn’t made a final decision about how to proceed, but that several legal, executive and legislative remedies were on the table.

Trump in an interview with Fox News broadcast on Monday night said the U.S. would “build tent cities” for migrants seeking asylum. “We’re going to put tents up all over the place. We’re not going to build structures and spend all of this, you know, hundreds of millions of dollars,” he added. “And they’re going to wait and if they don’t get asylum, they get out.”

Officials at the National Immigration Law Center, which participated in the earlier legal challenge to Trump’s travel ban, said they are prepared to fight a new order if Trump moves ahead. Marielena Hincapie, executive director of the center, said that the White House’s consideration of such action shows that Trump’s “racism-driven cruelty has no bounds.”

“We will use every tool to stop Trump from undermining the Constitution and international laws and from instituting his administration’s agenda to impose a Latin ban in any form,” Hincapie said in a statement.

But Peter Spiro, an immigration law professor at Temple University, said that courts could uphold the president’s potential actions. In June, a sharply divided Supreme Court upheld Trump’s ban on travel from the seven countries. The restrictions indefinitely bar more than 150 million people from entering the U.S.

The president has also threatened to cut off U.S. aid to El Salvador, Guatemala, and Honduras over the migrants heading toward the U.S. – though that could prove complicated. Much of the money for the three Central American countries was appropriated by Congress in the form of anti-corruption and good-governance programs. Those initiatives have broad support from lawmakers, who’ve already promised to put up a fight should Trump try to make good on his threat.