In her letter, which was made public yesterday by the group Human Rights in China, she explains that Gao was taken from the village of Xiaoshibanqiao (Shaanxi) on 4 February 2009 and has not been heard or seen ever since. She is especially distraught because of her husband’s health.

“I’m alone and isolated here and can only appeal to you to pressure the Chinese government to stop persecuting my husband and tell the world his whereabouts and condition,” the letter says.

Geng and her two children (pictured) fled China, paying human traffickers to smuggle them across the border by motorcycle. They arrived in Thailand after a harrowing journey across South-East Asia's mountainous terrain. They were accepted as refugees by the United States and flew stateside on 11 March 2009.

Gao Zhisheng was a member of the Communist Party and held in high regard as one of the best lawyers of the country.

Then he decided to defend miners, underground Christians and followers of the Falun Gong movement against the authorities.

In 2007 he wrote an open letter to the US Congress slamming China’s human rights violations.

He was then arrested, and tortured for weeks, enduring severe beatings, electric shocks to his genitals and cigarettes held to his eyes.

Several times in the past Washington has put pressure on Beijing on human rights.

Now Congress has to decide what to do.

It must do so against a backdrop defined by Secretary of State Hillary Clinton’s statement in her first official trip to China.

On that occasion she said that human rights in China should not distract from other vital issues for the United States like trade, the environment or the handling of the current global crisis which require close cooperation between the two powers.