US Senator Norm Coleman, a Minnesota Republican, who was later joined by five congressmen, in the past week called for the resignation of Annan, who has two more years in office before completing his second five-year term. They accused him of presiding over corruption in the UN oil-for-food programme for Iraq, administered by the United Nations but supervised by the 15-nation Security Council. After Coleman's statement, President George Bush pointedly refused to defend Annan, saying he wanted a "full and open accounting" of the now-defunct oil-for-food programme.

In reaction, the 191-member UN General Assembly gave Annan a standing ovation on Wednesday and the leaders of Britain, France, Germany, Russia and Australia telephoned the secretary-general to voice support. In an open letter on Thursday, a group of South African Nobel laureates - former president Nelson Mandela, Archbishop Desmond Tutu, and writer Nadine Gordimer - condemned attempts to have Annan resign. They said the real reason for the attack was "the admonishment by the secretary-general in respect of certain actions of the United States government in Iraq". Danforth again called for a thorough investigation. "The worst thing, to continue the cloud over an organisation, is to give the impression that something is being hidden or that there is not total cooperation," he said. "And that really is deadly in any kind of an organisation and that would have to be resolved." But he said, "Our view of the performance of the secretary-general is that he has done a good job, that he is doing a good job, that we have worked with him, that we anticipate working with him in the future. He noted Annan's help on the crisis in the Darfur region of Sudan and on planned elections in Iraq.

Danforth also played down reports that Annan's son, Kojo, had not fully disclosed his ties to a firm hired by the United Nations to inspect goods in Iraq. The younger Annan worked for the Swiss company Cotecna in West Africa. "The son is an adult and I think generally speaking there is a perceived difference and a real difference between adult children and parents," he said.

The oil-for-food programme, investigated by five US congressional committees, was launched in December 1996 and continued until 2003 to allow Baghdad to supply civilian goods to ordinary Iraqis, suffering under UN sanctions imposed in 1990. Most of the corruption revealed so far involves illegal transfers or smuggling of oil, which the Security Council, including the United States, knew about and controlled.