``Xu wrote a letter from prison which he gave to his lawyer, saying his supposedly open trial was mere political persecution,'' his wife He Xintong told AFP.

The letter, signed ``Xu Wenli, in shackles'', said ``political pluralism is historically inevitable'' and that history would judge fairly.

Xu wrote the letter during a visit by his state-appointed lawyer Mo Shaoping who had tried to persuade him to appeal within the allotted 10 days, he said.

``Xu said he would not appeal, attempt to defend himself, nor answer any questions from judicial authorities,'' she added.

Xu was sentenced to 13 years in prison by the Beijing No 1 Intermediate Court Monday for his involvement in the nascent opposition China Democracy Party (CDP).

Wang Youcai, 32, founder of the fledgling party received an 11-year sentence while Wuhan-based Qin Yongmin, whois also associated with the CDP, was jailed for 12 years.

``The purpose of the CDP... was not to overthrow the Communist Party but to supervise it,'' Xu said in his letter said.

``A small number of people in the Communist Party decided to crack down on the CDP'S activities because of their private vested interests in the one-party system.''

China, in a continuing crackdown on political dissent, handed down a 10-year jail term to Hunan labour activist Zhang Shanguang Sunday for ``endangering state security'', after he gave an interview to a US radio station about peasant unrest.

Dissidents and political observers say the government is being careful to hammer home a message of zero tolerance for political opposition as the country approaches a year which will mark the 10th anniversary of the 1989 Tiananmen Square massacre and the 50th anniversary of Communist China.

President Jiang Zemin warned last Thursday that China faced a precarious future as it entered 1999, and urged vigilance against attackson all fronts.

``Any factors that could jeopardise our stability must be annihilated in the early stages. This policy has been proved by our past experience,'' Jiang said.

His words, reported in the official media in the same week that Wang, Qin and Xu were sentenced, echoed his December 18 speech to the nation marking 20 years of economic reforms.

China ``must adhere to the four cardinal principles, have a clear-cut stand to fight against those factors disrupting social stability and nip them in the bud,'' he said.