But Raila Odinga, the leader of the Orange Democratic Movement (ODC), also blamed government militias for fuelling violence in the aftermath of the polls and called for mass rallies - a move that threatens more bloodshed.
Weary Kenyans, some hungry and homeless after a week of violence marked by ethnic clashes, prayed for peace on Sunday and urged their leaders to break the political deadlock.
Odinga, who claims Mwai Kibaki stole the presidential vote, told reporters on Sunday that he was ready to talk about sharing power, but only through a mediator empowered to negotiate an agreement that the international community would guarantee.
He welcomed the imminent arrival of John Kufuor,
Jendayi Frazer, the leading
Desmond Tutu, the South African Nobel peace laureate, also took part in the negotiations.
The explosion of violence has damaged the East African nation's image as a stable democracy and attraction for millions of tourists in a region wracked by wars, uprisings and civil unrest.
More than 350 deaths have been documented - though it is fear the toll could be much higher - and 250,000 have been forced from their homes in the upheaval over the disputed vote, only the second free election since
Blame game
Al Jazeera's Yvonne Ndege, reporting from
The troubles eased over the weekend, although there have been isolated machete fights and ethnic attacks, and police fired tear gas to disperse protesters in the coastal tourist town of
But more clashes are likely if Odinga presses ahead with his call for supporters to rally on Tuesday in defiance of a government ban.
Alfred Mutua, a government spokesman, said any such demonstrations would be illegal.
Attempts to hold opposition rallies last week were blocked by police who fired tear gas, water cannons and live bullets over people's heads.
Kibaki, re-elected by a narrow margin in a vote count that international observers say was deeply flawed, said on Saturday after meeting with Frazer that he was willing to form a unity government.
Odinga rejected that proposal, telling Al Jazeera's Mohammed Adow that "Kibaki knows very well he lost an election".
"I think it is like an insult to the people of
Coalition, not unity
But his spokesman Salim Lone said the party was open to other solutions.
"A government of national unity is not acceptable to us," he said. "But there are other formulations, such as a coalition government with genuine power sharing, that we are willing to discuss."
He said his party differentiates between a unity government, where the president has considerable power, and a coalition government that has greater possibilities for power sharing and where Kibaki need not necessarily even be president.
The other opposition proposal is to set up an interim government with a mandate to hold new presidential elections, he said.
Kibaki has said only a court could order fresh elections - an unlikely event since the judiciary is packed with his allies.
But it will be nearly impossible for Kibaki to govern without opposition support.
In a parliamentary election that was held the same day as the presidential election, Odinga's party won 95 of 210 legislative seats, and half of Kibaki's cabinet lost their seats – a sign of people's anger over perceived pervasive corruption and nepotism that favoured Kibaki's Kikuyu tribe.
Simmering resentment of the Kikuyus was ignited in the violence.
In the central Rift Valley that is Odinga's stronghold, thousands of Kikuyus fled their homes over the weekend, escorted by soldiers down roads strewn with corpses and burned out vehicles.
People queue to receive aid in