Kenya's opposition leader has called off nationwide rallies planned for Tuesday, following disputed elections.
The police had tightened security ahead of the planned rallies
Raila Odinga said he hoped international mediation could solve the crisis. He says the vote was rigged in favour of President Mwai Kibaki.
The top US official for Africa, Jendayi Frazer, has said Kenyans have been "cheated" by their political leaders.
The police now say that 600 people have died in election violence - up from the previous official figure of 350.
Some 250,000 people have fled their homes in clashes between rival political supporters, ethnic groups and the police.
The Law Society of Kenya has called for Mr Kibaki to step down, saying the election was "not credible" and the announcement of a winner "unacceptable".
After a week of clashes, some shops and businesses have re-opened in the capital, Nairobi and "matatu" mini-bus taxis have returned to the streets after several days when the city was deserted.
"We are now assured that the mediation process is about to start," Mr Odinga said after meeting Ms Frazer.
"We are therefore informing our supporters countrywide that there will be no public rallies [on Tuesday]."
Mr Odinga said Kenya was living through the gravest crisis it had faced and condemned the violence that had taken place.
Ms Frazer said there may have been vote-rigging by both sides and that ordinary Kenyans had been let down.
"They've been cheated by their political leadership and their institutions," she said.
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"The only way to restore the Kenyan people's rights and confidence in the system is that the political leaders have to stop the violence, because innocent people are dying."
Meanwhile, Mr Kibaki has reconvened parliament for 15 January.
Mr Odinga's Orange Democratic Movement won a majority in parliament but does not have the two-thirds needed for a vote of no-confidence in the president.
Both sides have accused the other of ethnic cleansing during a week of violence after Mr Kibaki was declared the winner.
A government ministry says 486 people have been killed but a senior police officers told the AFP news agency:
"We have at least 600 dead... some bodies are still in the bushes where fighting occurred."
Mr Odinga said he understood that Ghana's President John Kufuor, current chairman of the African Union, would also be going to Kenya soon for talks.
Last week, the government said there was no need for Mr Kufuor to go to Kenya.
Many in need
Mr Kibaki has offered to form a "government of national unity" but Mr Odinga says the president must step down.
The BBC's Peter Greste says there is no sign of this and there remains a large gap between the two sides' positions.
The government says it has deployed its military engineering unit to assist in unblocking the main highways to enable relief supplies to be delivered to displaced people, and for public transport to resume.
The head of the humanitarian services committee, Rachael Arunga, told a news conference in Nairobi that sufficient supplies were yet to reach thousands of displaced people in urgent need.
Ms Arunga said the Rift Valley province was the worst hit area and efforts were being made to deliver food items, tents and medicine to the displaced people.
Seven people were killed in a shoot-out at a police station on Sunday and there have been further clashes in Mombasa.
European Union observers have criticised the way some of the votes were counted, including anomalies between the results announced locally and nationally.