NAIROBI, Kenya — Kenya’s political crisis has taken a new turn with the chairman of the election commission — whose proclamation of President Kibaki’s victory triggered the violence that has killed at least 300 people — saying he doubted the result.

“I do not know whether Kibaki won the election,” Samuel Kivuitu said to the Standard, Kenya’s oldest newspaper on Tuesday, ahead of a critical rally by the opposition’s presidential candidate, Raila Odinga, due in Nairobi today.

“If this matter is finally taken to court, the ruling should be made urgently so that if it were decided that Raila is the president, so be it. If it is Kibaki, so be it,” said Mr. Kivuitu, whose comments amount to an extraordinary retreat from his confident announcement on Sunday that Mr. Kibaki had achieved re-election.

Mr. Kivuitu added that he came under pressure to release the results before he was ready. “I had thought of resigning, but thought against it because I don’t want people to say I’m a coward,” he said.

Five election commissioners have now questioned the credibility of the poll they supervised.

Both sides in the bitter struggle for power traded accusations. Mr. Kibaki’s government deliberately summoned memories of Rwanda’s mass killings in 1994 by accusing the opposition Orange Democratic Movement of conducting a “genocide.”

The killing in Kenya’s tribal fighting does not begin to compare with the 800,000 who died in the Rwandan atrocity. There is no evidence that any side intends to eradicate a given ethnic group, which is the legal definition of genocide.

But the lands minister, Kivutha Kibwana, said, “It is becoming clear that these well-organized acts of genocide and ethnic cleansing were well-planned, financed, and rehearsed by Orange Democratic Movement leaders prior to the election.”

Mr. Odinga’s spokesman, Salim Lone, adamantly denied this charge. “There’s genuine bloodshed, angry people killing each other, but the vast majority of people are being killed by the police,” he said to the Daily Telegraph.

Mr. Odinga’s planned rally in Nairobi today could trigger more violence. He has pledged to install himself as the “people’s president” by summoning a “million man march.” The authorities have banned the proposed gathering, which has already been postponed once.

“We cancelled last time because it was surrounded by heavily armed security forces, people would have come and they would have died,” Mr. Lone said. “But the government is refusing to allow us to assemble and I don’t know how long we can tolerate this.”

Foreign Secretary David Miliband of Britain and Secretary of State Rice issued a rare joint statement urging an end to violence and “an intensive political and legal process” to end the crisis. Britain has urged Mr. Kibaki to form a coalition with Mr. Odinga.

The government has formally rejected outside mediation, saying, “Kenya is not at war.” Nonetheless, President John Kufuor of Ghana, the chairman of the African Union, is expected to visit Nairobi. Mr. Kibaki has offered to meet Mr. Odinga and issue a joint appeal for calm, but the opposition leader has refused to talk to unless the president resigns.