Defense Secretary Jim Mattis announced Tuesday he will visit U.S. troops deployed to the Southwest border in Texas in support of border control agents trying to stop a caravan of thousands of Central American migrants from crossing to the United States.

“I’ll visit the border tomorrow,” Mattis told reporters before a meeting with the Qatari minister of defense at the Pentagon.

It will be the first time Mattis will visit the troops at the border that were ordered to deploy there last month. So far, more than 7,000 troops have been ordered to deploy to the southwest border across Texas, Arizona, and California.

They are not expected to come into contact with migrants but are helping to transport Department of Homeland Security (DHS) and the Customs and Border Protection (CBP) personnel, helping with building and reinforcing barriers at the border, and with planning and logistics, as well as medical and housing support.

As far as costs of the deployment, Mattis said he would update reporters as they become known.

“Obviously the units executing the border mission have got to report them up right up here. But we are capturing the costs,” he said.

CBP officials told reporters late October that there were at least two large migrant caravans headed to the U.S. — one consisting of approximately 3,500 migrants and another consisting of approximately 3,000 migrants.

On Monday, a caravan of nearly 400 migrants in eight buses arrived in the northern Mexican border state of Sonora, escorted by state and federal police, as Breitbart News’s Robert Arce reported. Sonora abuts Arizona but also Mexicali near the California border.

The migrants plan to head to the U.S. through Tijuana, which borders California, in hopes of avoiding more ruthless cartels along the Texas border, Breitbart News’s Ildefonso Ortiz and Brandon Darby reported Saturday.