U.S. President Donald Trump said his administration wants to accept a $400 million (£303 million) aircraft as a gift from Qatar, calling it "a great gesture" and he will be "stupid".

The potential move has been called "very illegal" by some members of rival Democrats - a point the White House denied - and it has drawn criticism from some Trump supporters.

Qatar itself earlier said the report on the plane was “inaccurate” and negotiations were still continuing.

The news came when Trump visited several countries in the Middle East, including Qatar.

The BBC Verification has been studying the legitimacy of a president who accepts gifts.

On Sunday, U.S. media reported that the Trump administration is preparing to accept a Boeing giant jet from the Catari royal family - saying the aircraft will be modified and temporarily used as Air Force One, the name of the aircraft used by the president.

Trump later released in the "Truth Society": "The Department of Defense is receiving free gifts from 747 aircraft to replace the 40-year-old Air Force One, temporarily, in a very open and transparent deal."

When the reporter was asked, Trump said: "This is a good gesture from Qatar. I am very grateful. I will never refuse such an offer."

In February, Trump said he was "not satisfied with Boeing" and he expected to get two delays directly from the company on the New Air Force One jet. He added that the White House could “buy a plane or take a plane or something.”

The Catari plane was filmed in February in Palm Beach, Florida, where Trump inspected it. According to its 2015 specification summary document, it currently has three bedrooms, a private lounge and an office.

A Katari official told CNN that the aircraft was sent to the Pentagon from the Katari Department of Defense (Pentagon) and will be modified to comply with Air Force One's safety and safety standards.

Experts say it could take years, meaning that the plane may not be ready for use until after Trump’s term is over.

Trump said the plane will go directly to his presidential library after leaving the office and that he "will not use it" after serving as president.

Still, the move has led to criticism from Democrats and some long-time Trump supporters, including Laura Loomer, who said: "If that's true, it's really going to be a taint to administrators."

Several senior Democrats claim that accepting gifts is illegal.

Democratic Senator Adam Schiff quoted a part of the U.S. Constitution that said no Congress approved it and no elected officials could accept "any field...any form" from foreign leaders.

Frank Cogliano, a professor of American history at the University of Edinburgh, said the clause “is intended to prevent bribery from affecting the government.”

"This is certainly expanding the constitution, and we haven't seen gifts of this size or nature yet," said Andrew Moran, a constitutional expert at Metropolitan University in London.

There are many other laws in Congress that are related to the acceptance of foreign gifts, such as the Foreign Gifts and Decoration Act of 1966, which means that only by accepting Congress’ consent can foreign gifts above a certain value.

Currently, U.S. officials can accept gifts worth less than $480 (£363).

Although Trump eventually mentioned the plane's "library", experts suggest that he does refer to his museum foundation.

Former presidents usually have a library with archives of their documents, often funded by private donations - filled with souvenirs and open to the public.

The fact that airplanes can be sent to the government rather than handed directly to the president before being transferred to a museum may not avoid potential violations of the Constitution.

Jordan Libowitz - a group that is responsible and moral from Washington - said any plane after Trump left the office would cross a line: "Reagan's Air Force One ended up in his presidential library, but there was a difference there. The plane was retired, Reagan never flew over it again, it flew over it again, it was inside the museum."

The U.S. Department of Justice reportedly drafted a memorandum explaining why it believes that acceptance of jets is permissible, although not yet publicly available.

When White House Press Secretary Karoline Leavitt was asked about the legality of the deal, “The legal details are still being made, but of course, any donation to the government is always fully compliant with the law.”

President Trump is in Saudi Arabia, Qatar and the UAE for four days, hoping to invest in the United States.

His visit comes after a series of business deals announced by the Trump Organization, which was run by the president's sons Eric and Donald Jr.

This includes plans to build golf courses and luxury villas in Qatar and the UAE.

President Trump is not yet affiliated with the Trump Organization and he handed over management responsibilities to his children after entering the White House on January 20.

The Trump Organization announced a deal in early May to develop a Trump-branded 18-hole golf course and announced a deal in a series of luxury villas in northern Doha, the capital of Qatar.

At the time, Eric Trump said: “With this extraordinary collaboration with Qatari Diar and Dar Global, we are very proud to expand the Trump brand to Qatar.”

DAR Global is a publicly owned Saudi construction company; Qatari Diar is a state-owned company in Katari.

In addition, on April 30, the Trump Organization announced that it would build "the first Trump International Hotel and Tower in the region" in "Heart of Dubai", which consists of 80-storey "Luxury Life and World-class Hospitality".

Eric Trump recently spoke at the 2049 Token 2049 of the Cryptocurrency Conference on May 1.

Asked if Trump could meet anyone involved in the family business on the road, White House press secretary Karoline Leavitt said it was "ridiculous" to suggest the president do anything for his own benefit.