Sen. Norm Coleman, who is leading one of five US congressional investigations into the UN oil-for-food program, wrote in Wednesday's Wall Street Journal that Annan should step down because "the most extensive fraud in the history of the UN occurred on his watch."

The Minnesota Republican joined several US newspapers and columnists in urging that Annan be replaced.

State Department spokesman Adam Ereli backed the congressional investigations but sidestepped the issue of Annan's resignation, saying "that is not something, frankly, that is in front of us."

Outside of Coleman's call, the secretary-general appears to retain wide support among the 191 UN member states who elected him to a second five-year term in 2001.

Russia, Britain, Chile, Spain and other nations on the UN Security Council strongly backed Annan in recent days, as did non-council members. The 54 African nations sent a letter of support.

"He has heard no calls for resignation from any member state," UN spokesman Fred Eckhard told reporters when asked whether he envisioned Annan's stepping down. "If there's some agitation on this issue on the sidelines ... that's healthy debate. But he is intent on continuing his substantive work for the remaining two years and one month of his term."