NAIROBI, Jan 8, 2008 (AFP) - Kenyan President Mwai Kibaki unveiled a partial cabinet Tuesday, sparking a fresh rift with opposition leader Raila Odinga as a key mediator flew in for talks on unrest that has left hundreds dead.

African Union chief John Kufuor arrived in Nairobi on a crucial mission to broker talks between the rival leaders in a bid to build on intense diplomatic efforts of recent days led by top US envoy to Africa Jendayi Frazer.

And after Kibaki and Odinga jousted with various proposals that might allow them to talk for the first time since violence erupted 10 days ago, leaving 600 dead and 250,000 displaced, US Secretary of State Condoleezza Rice asked Frazer to prolong her mission.

'The secretary asked her to stay in the region as long as she, Jendayi, could play a useful and helpful role,' Rice's spokesman Sean McCormack told reporters in Washington.

Kibaki briefly met Kufuor, the Ghanaian president, at the airport after naming part of his new cabinet in a televised address.

'In naming the cabinet, I have considered the importance of keeping the country united, peaceful and prosperous and a strong broad-based leadership,' Kibaki said.

Moments later, Odinga's Orange Democratic Movement (ODM) charged that the cabinet announcement was evidence of the president's unwillingness to negotiate a way out of the crisis triggered by last month's disputed presidential elections.

'The whole thing is a gimmick, the cabinet is a joke. We do not recognise the president and therefore we won't recognise his cabinet,' ODM secretary general Anyang Nyongo told AFP.

The opposition insists Kibaki's victory over Odinga in the December 27 elections was rigged.

In the western city of Kisumu, a police commander said officers fired into the air to disperse up to 300 young demonstrators who had blocked a road, lit bonfires and carried placards asking why the president named the cabinet.

The protests took place at the entrance to slums surrounding Kisumu city, a scene of recent deadly riots and an ODM stronghold.

Kibaki's partial line-up included two members of the Orange Democratic Movement-Kenya, led by third placed presidential contender Kalonzo Musyoka, who was appointed as vice president.

There was no slot for any member of Odinga's party.

Other appointments included key Kibaki allies, such as Uhuru Kenyatta, the head of the former opposition Kenya African National Union (KANU), as local government minister, and Moses Wetangula, from Kibaki's Party of National Unity, as foreign minister.

Attempts to bring Kibaki and Odinga together have so far failed, although the president had extended an invitation to his rival for face-to-face talks on Friday.

Odinga reject that the offer, saying he would only meet Kibaki with Kufuor's mediation.

'I have said we are going to meet under the chairmanship of Mr John Kufuor tomorrow (Wednesday) and I have said that the Friday thing is a sideshow to try to distract attention from the very serious efforts that are being made to resolve the crisis,' Odinga told a news conference Tuesday.

Four former African presidents were also in Kenya on Tuesday as diplomatic efforts accelerated to resolve the crisis.

Tanzania's Benjamin Mkapa, Mozambique's Joachim Chissano, Botswana's Katumile Masire and Zambia's Kenneth Kaunda travelled with US Assistant Secretary of State Frazer to western Kenya -- the region worst hit by the recent violence.

They visited some 1,000 people who sought shelter in a cathedral during tribal killings which swept the region after the announcement of Kibaki's re-election.

The United States is a key Kenyan ally and donor and President George W. Bush has urged the government and opposition to hold 'good faith' talks and end the violence.

With the New Hampshire primaries underway,Barack Obama's spokesman revealed Tuesday the frontrunning Democratic White House hopeful had called Odinga on Monday to urge both an end to violence and the start of unconditional talks.

Obama is 'trying now to speak with President Kibaki,' the spokesman, Bill Burton, told AFP.

Speaking to BBC radio, Odinga said he had spoken twice with Obama, whose father was from Kenya and like Odinga was a member of the Luo tribe, and added that he and Obama are relatives.

According to the United Nations, 250,000 Kenyans have been displaced by the violence and aid groups have warned of a potential health emergency in makeshift camps in schools, hospitals and churches in the isolated and still tense Rift Valley region of western Kenya, as well as Nairobi's slums.

The WFP said it had been able to deliver food aid to thousands of people in the western region, but its convoys still require police escorts on some stretches due to security concerns.

Ninety percent of tourist bookings for January have been cancelled, causing a revenue shortfall estimated at 46 million dollars (31 million euros), the Kenya Tourism Board said Tuesday.