Sky News US security agents are to be based at Heathrow and some other UK airports for the duration of the Olympic Games, according to Sky sources.
The Department for Transport has reached an agreement with the US Transportation Security Administration for specialist agents to be work at several UK airports.
They will arrive one week before the Olympics, and leave around a week after the end of the Paralympics.
Sky’s Home Affairs correspondent Mark White said: “This is an added security layer that has been done to help boost and aid the American airlines in particular that fly in and out of the likes of Heathrow and other airports.
“Nonetheless it is a very unusual occurrence and is significant.”
The move is aimed at helping US carriers in particular, but also UK airlines flying in and out of America.
The agents will not be allowed beyond boarding gates, or onto UK aircraft.
Olympic security is already under scrutiny after thousands of extra soldiers and police officers were drafted in to fill a gap left by private contractor G4S.
G4S has a £284m contract with the Government to provide 13,700 security guards for the Olympic Games, but only 4,000 guards are trained and ready.
The Government found out about the shortfall on Wednesday, and quickly had to boost the number of military personnel working on the Games by 3,500 to 17,000 – almost a fifth of the entire army.
Nine out of 12 police forces have been drafted in to help the embattled firm.
The forces providing additional personnel include Strathclyde, West Midlands, Thames Valley, Greater Manchester and Dorset.
Athletes started to arrive in the UK on Monday, on what was Heathrow airport’s busiest ever day.