The British government was forced to defend its security plans for next year's Olympics after a newspaper reported the US was set to send its own agents to the London Games.
The Guardian said US officials had raised "repeated concerns" about security and were planning to deploy 1,000 of their own security agents, including 500 from the FBI, in London.
The paper added the London Organising Committee of the Olympic and Paralympic Games (LOCOG) had underestimated the number of security staff it would need at the 32 Games venues, with 21,000 guards now required rather than the initial figure of 10,000.
Both the Home Office and the Ministry of Defence are involved in security planning for the Olympics.
A Home Office spokesman insisted that security planning was "on track" and that the International Olympic Committee (IOC) had "full confidence" in the blueprint.
"Security planning is on track and funding has been protected. The Government is committed to delivering a safe and secure Games that London, the UK and the world can enjoy," the spokesman said.