U.S. Military troops return from a test deployment with U.S. Customs and Border Protection agents after conducting a large-scale operational readiness exercise at the San Ysidro port of entry with Mexico in San Diego, California, U.S., January 10, 2019. REUTERS/Mike Blake

WASHINGTON (Reuters) - The U.S. military is set to deploy 3,500 troops to its mission at the border with Mexico, U.S. officials said on Thursday, bringing the politically charged deployment back to near its peak level of about 5,900 in November, if only briefly.

The figure was disclosed by House Armed Services Committee Chairman Adam Smith, who slammed senior Pentagon officials for failing to disclose that information during a hearing before his committee in Congress on the issue on Tuesday.

“This was at best an error in judgment, and at worst flat-out dishonesty,” Smith said, adding he had spoken with acting U.S. Defense Secretary Patrick Shanahan about it.

Shanahan told reporters the same day as the hearing that thousands more troops were headed to the border but the 3,500 figure was only disclosed on Thursday. There are currently about 2,350 troops involved in the border mission.

“I have followed up on that hearing with a phone call to Secretary Shanahan, and he has provided more details on the increase. I appreciate his willingness to discuss it with me, but a phone call is not a substitute for transparency before Congress and public candor,” Smith said.

The Pentagon says the U.S. military will operate mobile surveillance cameras in Arizona, California, New Mexico and Texas, a mission that is scheduled to run through Sept. 30. Some of the additional troops will also string up 150 more miles of concertina wire by March 31.

The Pentagon first approved the high-profile deployment of active-duty U.S. troops to the Mexico border in October, ahead of U.S. midterm congressional elections. It was embraced by Trump’s supporters, including Republicans in Congress.

However, critics have assailed the deployment as a political stunt and scoffed at Trump’s comparisons of caravans of Central American migrants, including women and children, to an “invasion.”