The Pentagon will deploy up 5,000 active-duty troops to the U.S.-Mexico border in an effort to prevent members of a migrant caravan from illegally entering the country, a U.S. official said Monday.

About 2,100 National Guard troops are already fanned out across the border under an order from President Donald Trump earlier this year. In recent weeks, the president has been warning repeatedly about the dangers posed by a caravan of mostly Central American migrants, which has swelled to an estimated 7,000 people and is continuing its slow trek north through Mexico.

Administration officials said last week that they were considering a plan to send up to 1,000 active duty troops to the border, but that deployment has increased to 5,000, according to the Department of Homeland Security official who spoke on condition of anonymity because he was not authorized to publicly discuss the plans before a formal announcement Monday afternoon.

The troops are not expected to conduct law enforcement activities, but instead provide backup support to Border Patrol agents manning the border and be prepared to react if groups of migrants try to storm the border.

The Homeland Security official also said the president is expected to deliver a speech on Tuesday to outline further actions to halt the migrant caravan, which could include limiting, or halting, the ability of migrants to request asylum. That move would be predicated on national security arguments similar to those used to enact Trump's travel ban last year, and would definitely meet the same legal challenges by immigration advocacy and civil rights organizations.

Those moves represent the latest in a series of efforts carried out by the administration attempting to show a robust response to the migrant caravan as the midterm elections draw closer. Department of Homeland Security Secretary Kirstjen Nielsen on Friday showed off a recently-completed section of border fence in Calexico, Calif., that including a plaque proclaiming the "completion of the first section of President Trump’s border wall." That section had been deemed a priority and funded during the Obama administration.

On the same day, Customs and Border Protection Commissioner Kevin McAleenan toured ports of entry south of San Diego and explained how additional troops would help secure the border from any attempted rush by the migrants to rush the border. But McAleenan, who described the oncoming caravan as a "law enforcement situation," conceded that despite the added manpower, his agency has no way to speed up the process by which migrants can legally request asylum.

That's what a majority of people did when the last migrant caravan reached the U.S. border in April — 122 were caught trying to enter the country illegally, but 401 presented themselves at ports of entry to request asylum, according to data from U.S. Citizenship and Immigration Services.