Kenya's opposition has warned it will relaunch mass protests in a week's time if talks do not break Kenya's political deadlock over disputed elections.
Kofi Annan did say the two rivals were very close to a deal
It demands parliament be recalled to pass constitutional changes that would allow a power-sharing agreement.
The opposition say MPs have one week to meet but the president remains opposed to any constitutional changes.
Violence over the dispute has left at least 1,000 people dead across Kenya.
However, most parts of Kenya are now calm.
Meanwhile, Nobel peace laureate Wangari Maathai told Kenyan reporters that she had received death threats from the banned Mungiki armed sect by text message.
Ms Maathai is a former minister and from the same ethnic group, the Kikuyu, as President Mwai Kibaki, but she has called for compromises by leaders on both sides since violence flared following the 27 December polls.
"Because of opposing the government at all times, Professor Wangari Maathai, we have decided to look for your head very soon. Chunga maisha yako (Take care of your life)," the text message read, she told reporters.
Former UN Secretary General Kofi Annan has been the chief mediator at the talks for a month. Last week he said the two sides were "very close" to a solution - but any deal now appears a long way off.
Ms Rice was the highest-ranking US official to visit since the election
Although both sides have agreed the idea of a grand coalition in principle, they appear deadlocked over how it should work in practice.
The opposition Orange Democratic Movement accuses the government of not being a serious partner in the negotiations.
The government accuses the opposition of bullying.
"As mediators, we are immune to intimidation or blackmail, we will continue as though they (the threats) are not there," government negotiator Mutula Kilonzo told reporters.
Opposition leader Raila Odinga wants powers to be vested in the new post of prime minister - but this needs MPs to amend the constitution.
President Kibaki's team has left several cabinet posts unfilled, opening the way for some form of coalition government - but remains opposed to the creation of a post of prime minister.
This was the issue that caused Mr Odinga to withdraw his support from President Kibaki several years ago.
US Secretary of State Condoleezza Rice urged both sides to reach a deal after holding separate meetings with President Kibaki and Mr Odinga on Monday.
"It can't be that there is simply the illusion of power-sharing, it has to be real, " she said.