NAIROBI, Kenya — Kenya’s opposition accused the government of backing away from plans to share power after a deeply flawed presidential election and called for nationwide protests, raising fears of new violence.

The two sides are engaged in lengthy and often bitter negotiations to end the deadlock over the December 27 vote, which the opposition says was stolen. Widespread fighting that killed more than 1,000 people in the weeks after the election has largely subsided, but this once-stable African country remains on edge.

The opposition Orange Democratic Movement filed notice yesterday giving police the required three days’ notice for a gathering planned Thursday. Past protests have descended into violence as police forced back crowds.

The party already had threatened mass protests if a deal is not reached by tomorrow, and yesterday’s filing was a clear sign its officials believe the talks could falter. A power-sharing deal between President Kibaki and opposition leader Raila Odinga seemed imminent last week, but the breakthrough never came. Yesterday, opposition negotiator William Ruto accused the government side of “changing their mind over sharing power.” He declined to offer further details. Government negotiator, Mutula Kilonzo, denied any change in position.

“This is not correct at all,” Mr. Kilonzo told the Associated Press, adding: “They thought this was a picnic where they would walk in and take over the government.” Mr. Kibaki was declared winner of the presidential vote, giving him a second five-year term, after Mr. Odinga’s lead evaporated overnight. International and local election monitors have said the results of the vote were manipulated, making it unclear who won. Negotiators for Mr. Kibaki and Mr. Odinga have agreed in principle to create a new prime minister’s post for the opposition, but are divided over just how much power such a post would carry.