Donald Trump has said he wants to scrap plans for a new Air Force One - labelling the project as "ridiculous".

The President-elect claimed the cost of converting a pair of 747 jumbo jets into a state-of-the-art command centre has exceeded US$4bn (€3.73bn), and called the expenditure "out of control".

On Twitter, he said the US government should cancel its order with Boeing.

Boeing is building a brand new 747 Air Force One for future presidents, but costs are out of control, more than $4 billion. Cancel order!

— Donald J. Trump (@realDonaldTrump) December 6, 2016

Speaking to reporters outside Trump Tower in New York, he later added: "I think it's ridiculous. I think Boeing is doing a little bit of a number. We want Boeing to make a lot of money but not that much money."

White House spokesman Josh Earnest questioned Mr Trump's figures, saying they "don't appear to reflect arrangements between Boeing and the Department of Defense".

The Pentagon estimates that the Air Force One replacement programme will cost US$2.87bn (€2.67bn) between 2015 and 2021, according to budget documents.

Boeing also has a US$170m (€158m) contract to conduct studies on the costs of building the plane with the requirements desired by the White House, including making it possible for Air Force One to communicate during a nuclear war.

In a statement, Boeing did not address Mr Trump's claims but said it would "deliver the best planes for the President at the best value for the American taxpayer".

Following Mr Trump's tweet, Boeing's shares dropped 0.7% to US$151.08 (€140.92). Shares of other major defence contractors also fell.

In July, Mr Trump hit out at President Obama and Hillary Clinton for using Air Force One on the campaign trail, calling it a "total disgrace".

He said: "Air Force One is a very old Boeing 747 and it sucks up a lot of gas, a lot of fuel. Boy, the fuel bill. You turn on those engines (and) I can tell you it's a lot of money."

During his own presidential campaign, Mr Trump travelled across the US on his private plane, a Boeing 757-200 that has been dubbed "Trump Force One".

Bob van der Linden, curator at the Smithsonian National Air and Space Museum, said there would be "very little likelihood" the US Secret Service would allow a serving president to charter a flight.

He said: "They would not know how the chartered plane was being maintained, they would have no control over it.

"Under the control of the Air Force it would be completely secure."

On Monday, the White House warned a phone call that took place between Donald Trump and Taiwan's leader had the potential to "undermine" relations between Washington and Beijing.

Air Force One v Trump Force One - how they stack up

Air Force One
:: Model - Boeing 747-200B
:: Passenger capacity - 102
:: Fuel capacity - 203,129 litres
:: Wing span - 59.64m (195.34ft)
:: Length - 70.66m (231.82ft)
:: Height - 19.33m (63.41ft)
Trump Force One
:: Model - Boeing 757-200
:: Passenger capacity - 43
:: Fuel capacity - 43,490 litres
:: Wing span - 38m (124.67ft)
:: Length - 54.4m (178.47ft)
:: Height - 13.6m (44.61ft)