The top US Africa envoy was Sunday due to meet Kenyan leaders in a bid to resolve an electoral row that touched off an unprecedented spasm of violence that has killed at least 360 people and displaced 250,000.
US Assistant Secretary of State for African Affairs Jendayi Frazer will try to seek consensus a day after President Mwai Kibaki offered to form a unity cabinet but opposition leader Raila Odinga defiantly demanded his resignation.
"She will hold follow-up talks on Sunday," a US embassy official told AFP.
After meeting Frazer on Saturday, Kibaki said in a statement that the unity government "would not only unite Kenyans but would also help in the healing and reconciliation process."
But Odinga stuck to his guns, insisting that Kibaki, who was sworn in for a second five-year term three days after the election, should step down before negotiations can begin for a solution to the country's worst political crisis in 25 years.
"Our starting point is that Kibaki is there illegally. He should not come to the negotiating table as the president: we want to talk with him on the basis of his old mandate then we find a settlement to this problem," he told reporters.
Meanwhile, African Union head and Ghana President John Kufuor won Kenyan approval to hold talks in Nairobi this week to "ensure that peace is maintained in Kenya," said Ghana's Foreign Minister Akwasi Osei Adjei.
The poll was marred by a delayed tallying process which observers have said was rife with irregularities and both sides have traded accusations of rigging.
The electoral board nevertheless declared Kibaki the winner, unleashing a wave of nationwide riots that quickly devolved into tribal killings, notably between Kibaki's Kikuyu tribe and Odinga's Luo.
At least 361 people have been killed in poll-related violence since Election Day, according to a tally compiled by AFP from hospitals, police and mortuaries.
Although the violence has receded, police on Saturday killed one man and injured three in the capital's Mathare slum after a group of young men sought to attack officers, a senior police commander told AFP.
Odinga's camp plans to hold a demonstration on Tuesday over vote rigging; nearly a week after police blocked its initial attempt. Its call for a presidential re-run in 90 days was rejected.
The UN estimates that the chaos may have displaced 250,000 Kenyans, some 100,000 of whom need immediate help in western Rift Valley region. The United Nations refugee agency UNHCR has pledged to provide aid.
Local aid workers fear an outbreak of diseases in makeshift camps in schools, hospitals and churches, most of which were still out of reach owing to their inaccessibility or safety concerns.
In a statement, the UN said the situation in the country is "calm but tense," and much of the capital Nairobi appears to be returning to "near normalcy."
"Even if the political situation is solved tomorrow, the force of the violence that was unleashed in recent days... has planted the seeds of a situation that could last much longer," UNICEF Kenya's chief communication officer Sara Cameron told AFP.
Despite the clashes in Nairobi, Police Commissioner Major-General Ali Mohamed Hussein said in a statement "the situation in the country is reverting back to normal."
In a letter to the archbishop of Nairobi, Pope Benedict XVI on Saturday pleaded for "an immediate end to acts of violence and fratricidal conflict."
Kibaki had been praised during the campaign for preserving Kenya's status as a war-free country and grooming its economy to become an "African tiger," but calls were growing for a probe into the ballot.
Kenyan Attorney General Amos Wako has suggested an independent audit, and Human Rights Watch warned that the country risked further violence in the absence of a transparent investigation.
A coalition of 27 leading Kenyan rights groups on Saturday rejected Kibaki's re-election, which they argued was rendered illegal by widespread voting irregularities.
"It is clear there were electoral anomalies. Unless justice is done, we might not find peace," said Anglican Church of Kenya chief Archbishop Benjamin Nzimbi.
Washington has considered the country a key ally and a beacon of stability in the restive region, and Frazer was expected to pursue consultations until Monday to try to break the deadlock.
The crisis has had an impact beyond Kenya's borders, with fuel shortages disrupting transport and trade in Uganda, southern Sudan, Rwanda and the eastern Democratic Republic of Congo.