Britain's hopes of drumming up $50 billion a year in aid for Africa suffered a serious setback on Friday when the United States rejected London's plan. Even Europe's backing seemed to be fading as both Italy and Germany said they would prefer something less ambitious than the proposal British finance minister Gordon Brown put to a meeting of the Group of Seven rich nations. But former South African president Nelson Mandela said he would accept no half measures. It was an outrage to let Africa sink further into disease and poverty, he said. "We are here to claim justice," the frail 86-year-old told the G7 ministers. "Do not delay while poor people continue to suffer," he said, demanding a full write-off of African debt and $50 billion extra a year in aid for the next decade. "I urge you to act tonight," said the political prisoner turned champion of democracy, invited to London to draw attention to Africa's plight. John Taylor, U.S. Treasury Under Secretary, rejected Brown's plan for what he calls an International Finance Facility (IFF) that would double existing aid by using rich countries' guarantees to raise money in the capital markets. --More 0043 Local Time 2143 GMT