WASHINGTON -- The United States has accepted a 747 jetliner as a gift from Qatar, the Pentagon said on Wednesday.

US Defense Secretary Pete Hegseth accepted the 400 million Boeing-made jet for use as US President Donald Trump's official plane, according to the Pentagon.

Accepting the plane has raised security and ethical concerns from both sides of the aisle, and experts have raised legal issues regarding gifts from foreign governments.

"Today marks a dark day in history: the president of the United States of America officially accepted the largest bribe from a foreign government in American history," Senate Democratic Leader Chuck Schumer said in a statement.

"This unprecedented action is a stain on the office of the presidency and cannot go unanswered," he added.

Trump has downplayed the ethical issues over the acceptance, saying it would be "stupid" to turn down the jet, while Qatar has dismissed concerns over the deal.

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

Retrofitting the luxury plane will require substantial security enhancements, experts say, which could cost hundreds of millions of dollars.