Approximately 1,100 Camp Pendleton Marines have been identified to assist Customs and Border Patrol Protection at the Southern Border as part of Operation Faithful Patriot, a Department of Defense spokesperson told NBC 7 on Sunday.

These Marines are engineers and trained in construction for the military, the spokesperson said. At this time, they remain at Camp Pendleton awaiting orders to report to the border.

Five San Diego military bases were selected by the DOD on Thursday to act as support installations, including Marine Corps Air Station Miramar, Marine Corps Base Camp Pendleton, Naval Base Coronado, Naval Base San Diego and Naval Base Point Loma.

The bases will be used for equipment and aircraft staging, the spokesperson said. It was unknown when they will be deployed and they could be deployed at a moment’s notice.

The deployment, named Operation Faithful Patriot, was in response to a caravan of migrants making their way hundreds of miles through Mexico to reach the United States' southern border.

President Donald Trump said Wednesday the number of military troops deployed could reach 15,000.

"We'll go up to anywhere between 10,000 and 15,000 military personnel on top of Border Patrol, ICE and everybody else at the border," he said.

DOD officials, however, told NBC 7, the number at this point is going to be closer to 7,000.

The migrants are about 800 miles from the nearest United States port of entry where they hope to seek asylum. It could be weeks or months before the migrants reach the U.S. border.

Similar caravans have occurred regularly over the years and passed largely unnoticed, but Trump has focused on the latest marchers seeking to make border security a hot-button issue in next week's midterm elections. The president has also threatened to close the border.

Asylum seekers already camping at border crossings worry that how the Trump administration responds to the caravan could leave them shut out.

In San Diego, people at the San Ysidro crossing wait more than a month, and volunteers operate an informal take-a-number system to spare migrants from having to wait in line or sleep out in the open. Inspectors there typically process about 100 claims a day.

Seeking asylum at a port of entry is legal under U.S. law, as government officials have reaffirmed this year. Trump has proposed banning people crossing illegally between ports of entry from claiming asylum — something many immigration experts say he can't do under the law.