About 4,000 U.S. troops expected to stay at Mexico border until end of January

The number of U.S. active duty troops at the southern border will drop from 5,600 to about 4,000, and their deployment will be extended through the end of January, under a new request from Homeland Security, U.S. officials said Friday.

Defense Secretary Jim Mattis is travelling and has not yet approved the DHS troop proposal. But military officials have been working with the agency on the request and it is expected to get approval.

U.S. President Donald Trump ordered the unusual deployment of active-duty troops to the border in response to a caravan of Central American migrants slowly north toward the U.S. Critics dismissed the deployment as a political stunt ahead of the midterm elections.

Most of the troops have been deployed in Texas, far from where the migrants eventually arrived in Tijuana, along the southern border with California. Soldiers have strung vast amounts of concertina wire and transported Border Patrol agents but have not been engaged in any law enforcement activities, which would be prohibited under U.S. law.

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The initial deployment was scheduled to end Dec. 15, but Mattis and other officials had said it could be extended. The new order extends it for 45 days while allowing about 1,600 troops to return home.

U.S. officials described the new request on condition of anonymity to discuss internal deliberations that had not yet been approved.

Officials said Friday that the troops staying at the border will provide support and protection for border patrol agents and continue to put up and repair wire barriers. In addition, more troops are expected to shift from Texas and Arizona to California.

As of Friday, 2,400 troops were deployed in Texas, 1,800 in California and 1,400 in Arizona.

According to officials, the troops staying at the border would include combat engineers who can install and repair the concertina wire barriers, helicopter crews to provide transportation, military police to protect U.S. forces and border patrol, and other service members to provide ongoing food, shelter and other support for the troops.

As of last week, the cost of using troops to help secure the border was estimated at $210 million, but this extension is likely to increase that figure.

That total included $72 million for approximately 5,900 active-duty troops providing support to Customs and Border Protection, plus $138 million so far for 2,100 National Guard troops who have been performing a separate border mission since April, according to a report sent to Congress early last week.