The file photo shows a fragment of a letter from China's Mao Zedong to former Labour Prime Minister Clement Atlee in 1937.

A letter written by China's Mao Zedong asking a leading British politician for help in fighting Japanese invaders in 1937 is to be auctioned later this month in London, where it is expected to fetch more than 100,000 pounds.

The letter, typed in English and signed by both Mao and Zhu De, one of the founding generals of the People's Liberation Army, was dated 1 November 1937 from Yan'an, a remote part of northwest China where Mao's forces had set up their headquarters in the fight against the Japanese invaders.

It is addressed to Major Clement Attlee, then leader of Britain's opposition Labour Party, and appeals for help in fighting the Japanese.

"We would ask you especially to lend the support of your party to any measures of practical assistance to China that may be organized in Great Britain.

"We believe that the British people, when they know the truth about Japanese aggression in China, will rise in support of the Chinese people, will organize practical assistance on their behalf, and will compel their own government to adopt a policy of active resistance to a danger that ultimately threatens them no less than ourselves,"the letter said.

Mao's original words were translated by James Bertram, a New Zealand-born British journalist who had been given an audience with Mao after helping smuggle the wife of one of Mao's colleagues across Japanese lines to Yan'an.

Britain joined the war against Japan in 1941 after the Japanese invaded British colonial possessions in South-East Asia.

Attlee became UK Prime Minister in 1945 and under his leadership, Britain became the first major western power to recognise the People's Republic of China on January, 1950; Atlee also became the first major western leader to meet Mao in a three-hour discussion over tea in 1954.

Historians believe Attlee played a major role in persuading US President Harry Truman not to declare all-out war on China during the Korean conflict.

Sotheby's will put the letter up for auction on 15 December, where it is expected to fetch between 100,000 and 150,000 pounds.

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