WASHINGTON, May 21 (Reuters) - The United States has

accepted a 747 jetliner as a gift from Qatar and the Air Force

has been asked to find a way to rapidly upgrade it for use as a

new Air Force One, the Pentagon said on Wednesday.

Secretary of Defense Pete Hegseth accepted the $400

million Boeing ( BA )-made jet for use as U.S. President Donald Trump's

official plane, the Pentagon said.

Pentagon spokesperson Sean Parnell said the Defense

Department "will work to ensure proper security measures and

functional-mission requirements are considered."

Legal experts have questioned the scope of

laws relating to gifts

from foreign governments that aim to thwart corruption and

improper influence.

Democrats

have also sought to block the handover.

Qatar has

dismissed concerns

about the aircraft deal. Trump has also shrugged off

ethical concerns, saying it would be "stupid" not to accept the

jet.

Retrofitting the luxury plane offered by Qatar's royal

family will require significant security upgrades,

communications improvements to prevent spies from listening in

and the ability to fend off incoming missiles, experts say. That

could cost hundreds of millions of dollars.

The precise costs were not known, but could be

significant given the cost for Boeing's ( BA ) current effort to

build two new Air Force One planes is over $5 billion.

The Air Force One program has faced chronic delays over

the last decade, with the delivery of two new 747-8s slated for

2027, three years behind the previous schedule.

Boeing ( BA ) in 2018 received a $3.9 billion contract to build

the two planes for use as Air Force One, thought costs have

since risen. Boeing ( BA ) has also posted $2.4 billion in charges from

the project.