WASHINGTON, Feb 2 (Reuters) - U.S. Defense Secretary

Pete Hegseth's first trip since taking office will be to the

United States' border with Mexico on Monday, in the latest sign

that fortifying the border will be a priority for the Pentagon

under President Donald Trump.

Trump has increasingly turned to the military to help carry

out his immigration agenda, including sending additional troops

to the border, using military aircraft to fly migrants out of

the United States, and opening up military bases to help house

them.

"POTUS wants 100% operational control of the border-and we

will deliver," Hegseth said on Sunday on X, referring to Trump,

as he announced the trip to visit troops on the border.

Trump declared a national emergency under the International

Emergency Economic Powers Act on Saturday, citing the

"extraordinary threat" from fentanyl and illegal immigration,

and imposed tariffs on Mexico, Canada and an extra duty on

Chinese goods.

Republican Trump last week said he was expanding a detention

facility at the U.S. naval base in Guantanamo Bay, Cuba, to hold

30,000 people. His White House border czar, Tom Homan, has said

he hopes to start moving migrants there within 30 days.

Additional U.S. Marines arrived at Guantanamo Bay in recent

days to prepare to expand a facility that holds migrants.

The Pentagon has also started providing flights for the

deportations of more than 5,000 immigrants held by U.S.

authorities in El Paso, Texas, and San Diego, California.

Two U.S. officials, speaking on the condition of anonymity,

said that U.S. military aircraft flew detained migrants to

Honduras and Peru over the weekend.

The military flights are a costly way to fly migrants.

Reuters reported that a military deportation flight to Guatemala

last week likely cost at least $4,675 per migrant.

That is more than five times the $853 cost of a one-way

first-class ticket on American Airlines ( AAL ) from El Paso, Texas, the

departure point for the flight.