Raila Odinga said he wanted to give mediation a chance, noting Ghana's President John Kufuor, the current chairman of the African Union, was expected soon on a mediation mission.
Odinga made the announcement at a news conference after meeting with U.S. envoy Jendayi Frazer and after the government said the proposed demonstrations were illegal and could provoke violence.
Kenyan government spokesman Alfred Mutua told reporters at a news conference Monday that the opposition Orange Democratic Movement was encouraging confrontation.
"It is unfortunate that while the ODM leaders are calling on their supporters to uphold peace, they are at the same time advocating a violation of the law and the creation of tension and hooliganism," he said.
Odinga called off the protests later Tuesday, reported the Associated Press.
President Mwai Kibaki was declared re-elected in Dec. 27 elections that critics say had a flawed vote tally, sparking a week of riots and ethnic clashes. The violence has damaged the East African nation's image as a stable democracy and attraction for millions of tourists in a region rent by wars and civil unrest.
At least 300 people were earlier estimated to have died, but a statement Monday from the Ministry of Special Programs raised the toll to 486 dead with some 255,000 people displaced from their homes.
The toll was compiled by a special committee of humanitarian services set up by the government which extensively toured areas most affected by riots and protests.
For more on how the crisis in Kenya has affected the country's citizens,for a story by CBS News reporter Katherine Arms in Nairobi.
Jendayi Frazer, the top U.S. diplomat on Africa, embarked on a final round of talks to help resolve the deadly dispute, meeting with Odinga, said U.S. Embassy spokesman T.J. Dowling. Odinga has signaled he is willing to share power with the government, which he accuses of rigging elections.
Odinga on Sunday called for mass peace marches and protest rallies across the country Tuesday to demand that Kibaki resign, a call that defies a new government ban on demonstrations.
Odinga advised his supporters to wear white arm bands to emphasize their peaceful intent and said any bloodshed would be the government's responsibility.
Attempts to hold opposition rallies last week were blocked by police who fired tear gas, water cannons and live bullets over people's heads. Human rights groups accused police of excessive force and unjustified killings in the crisis, but police Commissioner Hussein Ali insisted Sunday that "We have not shot anyone."
Frazer was on the last day of a three-day mission in which she has won an offer from Kibaki to form a coalition government and a concession from Odinga that he would negotiate without preconditions.
Odinga said Sunday he was willing to drop demands that Kibaki resign and was willing to discuss sharing power, but only through a mediator empowered to negotiate an agreement that the international community would guarantee.
He welcomed the imminent arrival of Ghana's President John Kufuor, current chairman of the African Union, who is expected in Nairobi by Tuesday.
Odinga said Kufuor was coming to mediate, but Mutua said the Ghanaian leader was on a fact-finding mission. "We are not at war, you mediate when you have warlords," Mutua said.
Adding to the pressure, Prime Minister Gordon Brown of Britain, Kenya's former colonizer, appealed Sunday for the two rivals to hold talks to end the deadlock over the country's second free election since independence in 1963.
Meanwhile, thousands of tourists have canceled vacations at the beginning of the high season.
"Hotels have been projecting an occupancy of 80-90 percent of capacity. But today, as we speak, that has dropped down to less than 40 percent. That's a huge loss for the economy," Mohammed Hersi, general manager of Whitesands Hotel in the coastal city of Mombasa, told AP Television News.
Schools were to reopen after the holidays on Monday, but the government postponed that for a week. Many are being used by refugees.
In Mombasa on Monday, a few dozen protesters gathered in the center of the tourist city yelling "No Raila, no peace!" Police in riot gear kept watch. On Saturday, police fired tear gas to scatter protesters there.
It would be nearly impossible for Kibaki to govern without opposition support.
In parliamentary elections held the same day as the presidential vote, Odinga's party won 95 of 210 legislative seats, and half of Kibaki's Cabinet lost their seats.
It was a sign of people's anger over pervasive corruption and nepotism that favored Kibaki's Kikuyu tribe. Simmering resentment of the Kikuyus was ignited in the violence, which pitted Odinga's Luo and other tribes against the Kikuyus.