President Donald Trump said he’s ready to deploy as many as 15,000 troops to the southern border of the U.S., triple the amount his administration announced a day ago, in a bid to stop or detain a caravan of migrants traveling north to the U.S.

Trump’s response to the caravan has escalated in recent days, along with his rhetoric on immigration, as crucial midterm elections near. The administration said Tuesday it would send 5,200 troops to the border by the end of this week.

“We’ll go up to anywhere between 10 and 15 thousand military personnel on top of border patrol, ICE, and everybody else at the border,” Trump said before leaving the White House for a campaign rally.

He has made illegal immigration a front-burner issue in the weeks before the midterm congressional elections on Nov. 6, believing it 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 said Tuesday that 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.

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