The US Air Force has begun modifying a Boeing 747 that was donated to the US by Qatar over the summer, an Air Force spokesperson said on Monday.

The plane will be used for “executive airlift support,” the spokesperson said.

President Donald Trump has said he wants to use the gifted plane as a new Air Force One.

Details related to the modifications being done to the plane and which company has been contracted to make the changes are classified, the spokesperson said.

CNN has previously reported that retrofitting and installing the required security and communications equipment on a second-hand plane from another government, even a friendly one, is a monumental task.

US spy and security agencies tasked with the overhaul will need to essentially strip the aircraft down to its frame and rebuild it with the necessary equipment.

The donation of the plane and the security risks it poses has prompted bipartisan criticism. Republican Sen. Ted Cruz said in May that it “poses significant espionage and surveillance problems.”

Across the aisle, Democratic Sen. Jack Reed, ranking member of the Senate Armed Services Committee, said accepting it would pose “immense counterintelligence risks by granting a foreign nation potential access to sensitive systems and communications.”

Air Force Secretary Troy Meink told lawmakers in June that it will “probably” cost the Air Force less than $US400 million ($599 million) to retrofit the plane.

That process could take anywhere from several months to two years, a retired senior military official previously told CNN.

While the Air Force would largely oversee the stripping of the Qatari aircraft and rebuilding it to meet security requirements, the project would also involve a slew of government agencies, including the Secret Service, Central Intelligence Agency, National Security Agency, and White House Communications Agency.

US-Qatari relations have been slightly strained in recent days following an Israeli strike on Doha last week that targeted senior Hamas officials. Secretary of State Marco Rubio will travel to Qatar as part of his current trip to the Middle East, a senior State Department official confirmed Monday.

The official did not provide further details about the stop, which comes after Rubio’s meeting with the Qatari Prime Minister last week and discussions with top Israeli officials this week.

Qatar has insisted publicly, however, that the US-Qatari defence relationship remains strong and denied that it is re-assessing the security partnership.

“The security and defence partnership between the State of Qatar and the United States is stronger than ever and will continue to grow,” Qatar’s International Media Office said in a statement on X last week.