The bitter rivals in Kenya's post-election dispute signed a peace deal today in an attempt to halt weeks of violence, the UN said, as the US secretary of state, Condoleezza Rice, prepared to personally intervene in the crisis.
Rice will visit Kenya for talks with the main players, the US president, George Bush, said.
No details have been officially released about today's deal, but the UN former secretary general Kofi Annan has called a news conference for tomorrow when the full text will be published. Talks are expected to continue next week.
However, a source told Reuters that today's talks ended badly and negotiators were consulting their leaders on what to do next.
Annan was leading talks between representatives of the president, Mwai Kibaki, who won the disputed election, and the opposition leader, Raila Odinga. The opposition insists the result was rigged.
In a statement, the UN said Annan would "outline what was agreed in 48 hours of discussion at a location outside the capital".
It added: "Mr Annan will make available the text of the agreement signed today between the two parties."
The Kenyan government's chief negotiator, Martha Karua, the justice minister, told Reuters: "Optimism is not the same as reality, but we are making progress."
Karua is seen by some as a hardliner who is unwilling to compromise with the opposition. Last month she corrected Kibaki after he called for a reforming grand coalition. She said such a suggestion had not been agreed within the government.
In a further bid to bid to end the violence, Bush said Rice would visit Kenya following their joint trip to southern and western Africa, which starts on Saturday.
Bush said: "There must be an immediate halt to violence, there must be justice for the victims of abuse and there must be a full return to democracy."
It was also announced today the rival factions have agreed to write a new national constitution within a year to make the country more stable and prevent repeat crises. It could enshrine power-sharing to diffuse future disputes.
On Tuesday it emerged that the opposition had offered to share power with Kibaki, in return for fresh elections in 2010. But since then there has been a news blackout on the talks in a bid to secure an agreement.
It is understood the ODM party has demanded more than half of the cabinet seats to reflect its vote in the parliamentary elections.
The talks were also moved away from the capital, Nairobi, to avoid the glare of the media. They are believed to be taking place at a safari lodge in the Tsavo West national park.
The row over December's disputed poll prompted weeks of unrest that has so far cost 1,000 lives and forced around 600,000 people to flee their homes.
Last week the opposition announced that a power-sharing deal had been struck. Annan branded the announcement "premature" but he agreed both sides had made significant progress.
It is unclear where the main opposition leader, Raila Odinga, stands on a power-sharing compromise.
Speaking to supporters in western Kenya on Saturday, he said Kibaki "must step down or there must be a re-election - in this I will not be compromised". On Sunday, Odinga said he was prepared for "giving and taking".