US accepts jet from Qatar for use as Air Force One

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 says.

Secretary of Defense Pete Hegseth accepted the $US400 million ($A621 million) Boeing-made jet for use as US President Donald Trump's official plane, the Pentagon said.

Pentagon spokesman Sean Parnell said the Defense Department "will work to ensure proper security measures and functional-mission requirements are considered".

He added that the plane was accepted "in accordance with all federal rules and regulations".

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.

He has defended it as a way to save tax dollars.

"Why should our military, and therefore our taxpayers, be forced to pay hundreds of millions of dollars when they can get it for FREE," Trump posted on his social media site.

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 current effort to build two new Air Force One planes is more than $US5 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 in 2018 received a $US3.9 billion contract to build the two planes for use as Air Force One although costs have since risen.

Boeing has also posted $US2.4 billion in charges from the project.

with AP