William Hague has insisted that Britain will remain America's most important military ally despite swingeing cuts to the defence budget.
In a speech in Washington, the Foreign Secretary sought to allay concerns that the UK's ability to respond to future threats would be diminished and the "special relationship" undermined.
He maintained that Britain "still packs a punch" and that the coalition Government would not allow any decline in the UK's role in the world.
"We are confident that Great Britain is equipped to face the security challenges of the next decade and beyond, and to stand firm with its allies," he said at Georgetown University.
"We have a clear long-term vision of Britain as an active global power and the closest ally of the United States."
He added: "Britain will remain a first rate military power and a robust ally of the US and in Nato well into the future."
Last month's strategic defence and security review was studied carefully in Washington amid fears about its implications for future conflicts.
It heralded an 8% reduction in defence spending over the next four years, which will see 17,000 armed forces personnel cut, Harrier jets scrapped and the HMS Ark Royal decommissioned.
Mr Hague said there was a "mistaken idea" that the Government was sacrificing national defence to reduce the UK's massive budget deficit.
Instead, the cuts would enable the UK to be even stronger in the future as its economy grows, he said.