The offer, made three years before Britain exploded a home-produced bomb, was said by the document to 'reflect Pentagon opinion' that Britain might be vulnerable to a Soviet invasion and that its secrets might fall into enemy hands.
The deal was proposed by General Eisenhower, then chairman of the US Joint Chiefs of Staff, to General Sir William Morgan, commander of the British Army Staff in Washington. It is not clear from the document whether the offer - which was refused - was ever considered by the Cabinet.
The document, marked 'Top Secret', records a meeting of the Chiefs of Staff in February 1949. It became available at the Public Record Office in 1980, but has been overlooked until now.
At the meeting, Morgan referred to a conversation between himself and Eisenhower, in which the offer had been made. The document says: 'General Morgan said . . . that General Eisenhower had quite clearly proposed that the United Kingdom might abandon its atomic energy programme in return for a number of bombs.
'The opposition in America to the development of atomic energy in the United Kingdom was centred on the views of the military authorities, who were inclined to exaggerate the possible dangers that might beset Britain.'
John Kent, the London School of Economics historian who found the document, said: 'The Americans were worried about the geographical location of Britain. They knew that if war broke out with the Soviet Union, western Europe would have to be abandoned. Britain could not be defended against being overrun by the Soviets. Its nuclear secrets would be lost.'
Historians have long known that the the US wanted to be the only power able to manufacture nuclear weapons after the Second World War, even though British and American scientists had collaborated on the first bomb. The Americans hoped that Britain would be satisfied with access to US bombs, still under US control, in time of war.
But the revelation that the Americans were prepared to buy Britain's acquiescence with bombs under British control is entirely new, according to Nicholas Wheeler, a specialist in the field at Hull University.
'The implication is that they were offering bombs that could be fitted into British planes, and used for British targeting priorities - which surprises me,' Dr Wheeler said. 'It is significant because it shows just how worried the Americans were. They really did not want Britain to develop its own programme, both for commercial reasons and because of the problem of international control.'
Dr Kent said the British refused the offer because they were determined, with or without American approval, to develop a bomb on their own. 'British policy after the war was obsessed by the pursuit of independent 'Great Power' status. If they had accepted Eisenhower's offer, it would have shown they were dependent on the Americans.'
Even if the offer had been accepted, it might not have been possible to implement it, according to John Simpson, of Southampton University. Although the offer 'reflected Pentagon opinion', US atomic policy was largely controlled by the hawkish US Congress, which had passed legislation in 1946 forbidding collaboration on nuclear matters with any other country.
Dr Simpson said: 'If there had been a deal, it would have had to be one that (Congress) was prepared to go along with. And the legislation said no one could even talk to the British over a deal.'
Even when Eisenhower became President in 1953 - after both the Soviet Union and Britain had tested their own bombs - Congress would not let him negotiate with Britain over nuclear research.Reuse content