"I'm not ready to contemplate failure. I'm not ready to give up now, and the team working with me are of the same spirit," Annan told Britain's BBC radio. "We cannot afford to fail."

Annan, who has met President Mwai Kibaki and opposition leader Raila Odinga to try to end violence that erupted after a disputed election in December, said he expected the country's political leaders to give way in their standoff.

"It always begins with intransigence. But then one begins to encourage them to move and shift. And there have been some shifts. Perhaps not enough, but we will get there. They will have to shift. They will shift," Annan said.

Official results pronounced Kibaki the winner and he was sworn in for a second term, but Odinga and his followers say the results were falsified.

Hundreds of Kenyans have since died in violence, often between members of Kibaki's long-dominant Kikuyu tribe and other tribes whose followers support Odinga. Annan acknowledged there had been an ethnic component to the bloodshed.

"I think there is a gross and systematic abuse of human rights, and there have been ethnic overtones, where there have been attacks and then revenge attacks. But if it's brought down quickly I think we will be able to stem the mayhem and the killing and the murders that have been going on," he said.

He said he believed ordinary Kenyans were tired of the violence and would persuade their leaders to reach an accommodation.

"There has been a failure of leadership because at certain levels they should have anticipated some of the events. The signals have been around for a long time," he said.

"The people are traumatised. They are angry. They are upset with their leaders, and if anyone remains recalcitrant and difficult, I don't think the population will accept it. The average citizen of Kenya will know who to blame.

"And I don't think people who are ambitious and believe they have a political future would want to place themselves in that position."