China's best known rights lawyer, Gao Zhisheng, whose case is a sore point in Sino-U.S. relations, was allowed a visit from his family last weekend, the first time he has been seen for nearly two years, his wife said on Wednesday.

The treatment of Gao, whose secretive detention has also drawn criticism from the U.N. human rights body, is one of the thorniest human rights disputes between China and the United States.

Senior Obama administration officials have raised it with Beijing, and the U.S. State Department has called on China to immediately release Gao and clarify his whereabouts.

His wife Geng He, who fled to California with the couple's children, told Reuters by telephone that Gao met his elder brother and her father last Saturday at the Shaya County prison in far western region Xinjiang.

The elder Gao told Geng her husband appeared to be paler than usual, but was in good physical condition.

The supervised visit, which lasted around 30 minutes, gave Gao no chance to say where he has been for the past two years, or talk about his treatment in jail.

I said: 'Brother, why didn't you ask him ... where was he staying? Where was he all the years before? Geng said. (His) elder brother said: 'My main purpose of the trip is to determine whether he's alive or dead. The police will not allow you to ask so many things.'

Gao's elder brother, Gao Zhiyi, declined to comment.

Gao, who wept after he asked about his father-in-law's health, told his elder brother: As I'm in such a state, I can't take care of all of you, so please take care of yourselves, according to Geng.

A combative rights advocate who tackled many causes opposed by the ruling Communist Party, Gao was sentenced in 2006 to three years in jail for inciting subversion of state power, a charge often used to punish critics of one-party rule.

He was put on probation for five years, formally sparing him from serving the prison sentence, but his family was kept under constant surveillance and he was sporadically taken into custody during that period.

Last December, state media reported that Gao was back in jail, in what was the first official account of his whereabouts in the last year.

Geng, who has not seen her husband since January 2009, said she has hired two lawyers to appeal against his punishment, and they could start the process in May.

Gao was taken from a relative's home in Shaanxi province in northern China in February 2009. He resurfaced briefly and made contact with friends and foreign reporters in April 2010.

(Reporting by Sui-Lee Wee)