The US has made an eleventh hour intervention in the highly charged defence review as Britain's top military brass launched a last ditch attempt to persuade David Cameron to water down the cuts.

Hillary Clinton, the US secretary of state, and Robert Gates, the defence secretary, both voiced concerns about the planned cuts as the heads of Britain's three armed services marched into No 10 in uniform to express unease about plans to cut the Ministry of Defence budget by 10%.

As the prime minister welcomed General David Petraeus to Downing Street, Washington highlighted concerns that Britain will scale back military spending to the level of weaker Nato members.

In an interview with BBC Parliament's The Record Europe in Brussels, Clinton was asked whether she was worried about the planned cuts in Britain. "It does, and the reason it does is because I think we do have to have an alliance where there is a commitment to the common defence. Nato has been the most successful alliance for defensive purposes in the history of the world I guess, but it has to be maintained. Now, each country has to be able to make its appropriate contributions."

Gates, who was in Brussels for a meeting of Nato defence ministers, voiced similar concerns. "My worry is that the more our allies cut their capabilities, the more people will look to the United States to cover whatever gaps are created," the defence secretary told Bloomberg en route to Brussels. "At a time when we are facing stringencies of our own, that's a concern for me."

As the deadline for the completion of the defence review approaches, Britain's top brass donned their uniforms to march across Whitehall and into No 10 to raise their concerns in person with the prime minister. Admiral Sir Mark Stanhope, the first sea lord, Air Chief Marshal Sir Stephen Dalton, the chief of the air staff, and General Sir Peter Wall, the chief of the general staff, are all understood to have warned that the cuts could endanger the future of Britain's armed forces. Air Chief Marshal Sir Jock Stirrup, the outgoing chief of the defence staff, also attended.

The service chiefs are also understood to be concerned about the prime minister's decision to appoint his own military adviser. It is understood that they feel that the appointment of Colonel Jim Morris, of the Royal Marines, could jeopardise the position of General Sir David Richards, the incoming chief of the defence staff, as the prime minister's principle military adviser. Richards did not attend the meeting because he is abroad.

A Downing Street spokeswoman said: "Hillary Clinton was talking about defence cuts across Europe and specifically in the context of Nato. She is absolutely right when she says that each country has to be able to make its appropriate contribution to common defence in Nato and Britain will always do that."