The authorities say that security has improved, but the internal security ministry said politicians must use demonstrations to "promote peace and national reconciliation".
Earlier, negotiators had denied that the political parties had reached a "breakthrough" in efforts to solve the dispute over the December 27 polls.
The fallout over the elections led to riots and ethnic attacks that killed more than 1,000 people and displaced hundreds of thousands more.
The opposition maintains that the presidential election, won by Kibaki, was rigged.
Negotiators said talks had moved forwards, but a final deal is yet to be reached.
William Ruto, an opposition leader, said: "There is positive news, but no final solution yet."
|Annan says patience is needed [EPA] |
Ruto denied earlier media speculation that the two sides had agreed to share power in a government of national unity, saying: "I don't think so. That is not the case."
Separately, Mutula Kilonzo, a member of the government's negotiating team, said that a solution was imminent.
"It is not complete yet, but the progress is excellent", Kilonzo said.
Negotiators for Kibaki and Odinga have quickly agreed on principles to end the violence and help refugees, but they have yet to agree on the issue of who won the election and what should happen next.
Both sides have accused each other of rigging the December vote.
For several weeks the government had argued that the opposition would have to challenge the results through the courts.
The opposition rejected a legal challenge, saying the courts were not independent.
Doctors Without Borders (MSF) says that Kenya could face food shortages and a breakdown of health services in the coming months.
Filipe Ribeiro, MSF's emergency aid co-ordinator for Kenya, said that the displacement of Kenyan's will have an impact on both urban and rural areas.
"The fact that people are pouring into slums where the population already is struggling to cope will cause a big problem for food security in urban areas," he said.
"We will be closely watching the food situation in the months to come."
He noted that no work is being done in the fields of Western Kenya during planting season.
He recalled that during similar upheavals in 1992, it took three years to "bring to an end displacements, camps and resettlements" across the country.