WASHINGTON (AFP) - The United States has revoked the travel visa of a Pakistani rights defender ahead of her trip to Washington to highlight the plight of hundreds of missing compatriots allegedly rounded up as part of the 'war on terror', the rights group Amnesty said. Amina Janjua, founder of Defence of Human Rights, was about to take a flight from Geneva to Washington Saturday when she was informed by a US diplomat by telephone that the visa issued to her had been cancelled, an Amnesty official said. "It is extremely unfortunate that the United States revoked her visa," Amnesty's Washington-based Asia-Pacific director for Advocacy T Kumar told AFP. "We hope they would reconsider the decision," said Kumar, who was also informed by the US diplomat about the visa's cancellation. Amnesty had arranged Janjua's week-long US trip and had confirmed her meetings with senior State Department officials and congressional staff, Kumar said. US officials were not immediately available for comment. Janjua has visited Norway, Sweden, Germany and Switzerland as part of her tour to raise awareness of what Amnesty calls 'enforced disappearances' by the Pakistani government since it joined the US-led war on terror in 2001. Her husband is among 563 people who had disappeared, according to Defence of Human Rights. Amnesty said they were arbitrarily detained and held in secret facilities mostly for suspicion of links to terrorist activity. Some were also secretly handed over to the US authorities, often for financial reward, ending up in US Navy-run prison in Guantanamo Bay, Cuba, and secret CIA detention centres, Amnesty said. The group said it had used official court records and affidavits of victims and witnesses of enforced disappearances to confront the Pakistani authorities, who have denied any knowledge of their whereabouts. Janjua herself has presented to the Pakistan Supreme Court with an affidavit from five people declaring that her husband, who went missing in 2005, was held at various places of detention by the country's intelligence agency.