Trump says Qatari-gifted Air Force One will receive full security upgrades

US President Donald Trump says his new Air Force One aircraft will undergo further upgrades after reports questioned its security capabilities.

Speaking to reporters on Sunday after returning from the World Cup final in New Jersey, Trump said the Qatari-gifted Boeing 747-8 would soon be sent away for additional work.

"It has a lot of capability, but as I understand it, in about a month or so, they're going to send it to have it be maxed out. So they're going to be sending it, and they'll have it be maxed out. It'll take about a month," Trump said.

The comments came after The New York Times reported that the aircraft lacked some of the defensive systems fitted to the traditional presidential aircraft, including anti-missile technology.

THe newspaper also reported that its journalists were later subpoenaed by the Trump administration.

Trump did not provide further details about the planned upgrades.

The aircraft was donated by Qatar's royal family after Trump criticised the ageing presidential fleet. It features a new red, white and navy blue paint scheme chosen by the president.

The gift has drawn criticism from opponents, who have raised ethical, constitutional and national security concerns over accepting an aircraft worth hundreds of millions of dollars from a foreign government.

Two newly built Boeing Air Force One aircraft are expected to enter service later this decade following years of delays.