His wife, Geng He, sneaked out of China in early 2009 with their two children, journeying by foot to Thailand before escaping to the United States. She has since kept a low profile but traveled Tuesday to Washington as Chinese President Hu Jintao arrived for a closely watched state visit.
"I want him to release my husband immediately so our whole family can be reunited," Geng told AFP. "I am hoping that I can get my message out."
Geng pleaded for Obama to ask Hu about her husband, pointing to the US leader's own writings about growing up with an absent father.
"My 17-year-old daughter and my seven-year-old son miss their father very much. It has been so painful for them," she said.
"Maybe when you missed your father, you knew where he was. But my children don't know where their father is right now. Maybe he's no longer alive or maybe he's being tortured by many people right now."
Geng was visibly nervous as she prepared for a week of speaking out about her husband, but said: "My husband is worth it. I need to do this for him."
"My husband is a lawyer. He always fights for the suppressed, the minority groups, the persecuted. Power and money will not be able to tempt him to change his principles," she added.
"I think any lawyer like this deserves help from all of us."
Gao, during his brief reappearance in April, said he was stripped naked and violently pistol-whipped for two days in September 2009. He said the beating was even worse than during a previous disappearance, when he said he suffered electric shocks to his genitals and cigarette burns to his eyes.
"You must forget you're human. You're a beast," Gao said his jailers told him, according to an interview he gave to The Associated Press.
The news agency said Gao asked that the account not be published unless he went missing again or found safe haven abroad.
His wife said she had been fearing the worst about Gao. She said his brother saw him last April and told her that "he has been through death."
Obama invited Hu for a state visit, which will include a red carpet welcome at the White House and a lavish dinner, part of a US effort to broaden cooperation between the world's largest developed and developing nations.
White House spokesman Robert Gibbs insisted that the warm welcome would not mute US appeals to China to improve its human rights record.
Human rights groups have roundly criticized the Obama administration on China, particularly Secretary of State Hillary Clinton's statement after taking office that rights concerns would not "interfere" with cooperation.
But Clinton said Friday that human rights were at "the heart" of US diplomacy and insisting that China, as a founding member of the United Nations, "has committed to respecting the rights of all its citizens."
Clinton explicitly called on China to improve treatment of minorities and free dissidents including Gao and the writer Liu Xiaobo, who won the Nobel Peace Prize in absentia last month.
Bob Fu, the founder of Christian rights group China Aid who brought Gao's family to the United States, welcomed Clinton's speech as a new tone by the administration but disagreed with its overall assessment of ties with China.
"As long as Mr Gao Zhisheng is still missing and brutally tortured simply for promoting human rights and the rule of law, it's not appropriate to call that regime an equal partner," Fu said.
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