In his first orders as Pentagon chief, new Acting Defense Secretary Richard Spencer signed off on sending 2,100 more troops to the southern border to back up law enforcement in stemming illegal crossings and dealing with asylum seekers, the Defense Department announced.

In response to a Department of Homeland Security request, Spencer on Tuesday night approved the deployment to the border of 1,000 Texas National Guard troops, who will remain under the command of Gov. Greg Abbott, Pentagon spokesman Maj. Chris Mitchell said in a statement.

In addition, Spencer approved increasing the presence of active-duty troops on the border by 1,100 personnel over the next several weeks, according to Mitchell. The statement gave no indication of the units from which the active-duty troops will be drawn.

The deployment approvals were the first significant actions taken by Spencer since he took over as acting defense secretary late Monday afternoon in the latest reshuffling of the Pentagon's top leadership.

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Spencer, who had been serving as Navy secretary, replaced then-Acting Defense Secretary Mark Esper, who had to relinquish the post under federal law when the White House finally sent formal notification to the Senate of his nomination to the permanent post as defense secretary Monday afternoon.

Esper went before a Senate Armed Services Committee confirmation hearing Tuesday; a vote by the full Senate on his nomination could come later this month. Spencer is expected to return to his post as Navy secretary if Esper is confirmed.

At an April event with supporters in Texas, President Donald Trump said he was considering sending more troops to the border to bolster security against the flow of migrants.

"I'm going to have to call up more military" to deal with the crisis, which has resulted in overcrowded border facilities and family separations, he said.

About 5,000 military personnel are currently deployed for the border mission -- about 3,000 active-duty troops and 2,000 National Guard, according to the Pentagon.

Their mission limits them to support of Homeland Security operations by reinforcing barriers and providing logistics and aerial surveillance support. They are not allowed to engage directly with or detain migrants under the current rules.

The Pentagon announcement Wednesday said that about 750 of the newly deployed Texas National Guard troops will back up Customs and Border Protection (CBP) personnel at temporary adult migrant holding facilities in Donna, Texas, and Tornillo, Texas.

Another 250 Texas National Guard troops will provide support to CBP at port-of-entry crossing points and at Texas airports "to enhance border security and improve the flow of commercial traffic," the Pentagon said.

Mitchell's statement suggested that decisions on whether the Texas National Guard troops will carry weapons will be left to Abbott's discretion.

"Decisions regarding arming military personnel and related rules for the use of force will be informed by the circumstances of their mission and be made by the governor of Texas, in consultation with CBP," Mitchell said.

The additional 1,100 active-duty troops being sent to the border over the next several weeks will deploy "in support of CBP's Operation Guardian Support mission with aerial surveillance, operational, logistical, and administrative support," he added.

-- Richard Sisk can be reached at Richard.Sisk@Military.com.