Britain and the United States discussed the possible use of nuclear weapons against China if it moved to seize Hong Kong during the Cold War, according to documents released Friday.

Some leaders in London thought the only way to keep Hong Kong a British colony was to convince China that any attempt to take the territory back by force would trigger American nuclear attack, according to the internal British government memos declassified and released by the National Archives.

'Our objective is to encourage the Chinese to believe that an attack on Hong Kong would involve U.S. nuclear retaliation,' Defense Minister Harold Watkinson wrote in a letter to Foreign Secretary Alec Douglas-Home and Prime Minister Harold Macmillan.

Hong Kong became a British colony in 1842, and was returned to China in 1997.

Watkinson was advising Douglas-Home and Macmillan on the approach he thought should be taken by Lord Louis Mountbatten, chief of the defense staff, in talks with Adm. Harry Felt, then the commander of U.S. Pacific forces.

The U.S. and British officials discussed the issue in Hawaii in 1961, according to the documents. There is little in the records to suggest to what degree such an option might have been considered.

Mountbatten, in his report on the meeting in Honolulu in March 1961, said Felt asked what Britain expected the United States to do if China attacked the colony.

'I replied that this depended on whether the Americans minded whether we lost Hong Kong or held it. He replied that he did not see that he could do very much except bomb the Chinese,' Mountbatten said.

Douglas-Home said in a 'Top Secret' letter dated Feb. 22, 1961 to Watkinson that, 'It must be fully obvious to the Americans that Hong Kong is indefensible by conventional means and that in the event of a Chinese attack, nuclear strikes against China would be the only alternative to complete abandonment of the colony.'

Two years earlier, Cabinet Secretary Norman Brook wrote to the prime minister that Britain was concerned about Hong Kong's vulnerability.

'Hong Kong is no longer of vital strategic importance to us,' Brook wrote. 'But it has symbolic and political importance and is our only direct frontier with the Communist world. For political reasons we have no choice but to stay there at present; though at any time the Chinese could make conditions so impossible by cutting off food and water supplies and strangling trade as to make our presence virtually untenable.'

Graham Allison, director of Harvard University's Belfer Center for Science and International Affairs, said the documents were 'a hard reminder of the psychological and conceptual frame of the time during which the U.S. had nuclear weapons all over Europe and standing plans to use them if the Soviet army marched west.'

'At the time, people in the West thought of China as very aggressive and allied with the Soviet Union,' Allison said in a telephone interview.

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