Reuters reported that two ZANU-PF party sources said on Tuesday the projection showed Tsvangirai falling short of the 51 percent needed for outright victory. The party's numbers appeared to be in line with projections by an independent monitoring group.
The stunning political developments were followed by reports in the New York Times that advisers to President Mugabe were in talks with Tsvangirai about the long-time strongman's resignation, according to a Western diplomatic source and a Zimbabwe political analyst.
Marwick Khumalo, head of the Pan-African Parliament observer mission, also indicated the ruling ZANU-PF party was considering the possibility of defeat.
"I was talking to some of the big wigs in the ruling party and they also are concerned about the possibility of a change of guard," he told South African Broadcasting Corp.'s SAfm radio, according to the Associated Press.
"ZANU-PF has actually been institutionalized in the lives of Zimbabweans, so it is not easy for anyone within the sphere of the ruling party to accept that 'maybe we might be defeated or might have been defeated,"' he added.
No official results have been released for Saturday's presidential poll. It took the Zimbabwe Electoral Commission 30 hours to release results for 132 parliamentary seats -- raising fears that some within Mugabe's government could be attempting to rig the results in an attempt to stay in power.
"We have won an election. Mugabe's victory is not possible given the true facts," Tendai Biti, secretary-general of Tsvangirai's party, told reporters Monday.
Two senior government sources, who asked not to be named, told Reuters their projections showed Tsvangirai getting 48.3 percent, against Mugabe's 43 percent, with a third candidate taking eight percent.
"What this means is that we are looking at a re-run because he did not win with a margin of over 51 percent that would have given him the job straight away," one of the sources said.
Mugabe, 84, has faced intense domestic pressure because of Zimbabwe's economic collapse and an increasing strong political opposition. Zimbabwe is suffering the world's highest inflation of more than 100,000 percent, 80 percent unemployment, chronic shortages of food and fuel and an HIV/AIDS epidemic.
Tsvangirai, 56, narrowly lost disputed 2002 elections, and the opposition said it would take to the streets in peaceful protest if this year's vote was rigged.
Britain, Germany and the EU called for faster reporting Monday to ease tension, while the United States urged Zimbabwe to "do the right thing" as it counts the votes. State Department spokesman Tom Casey said the United States "strongly encourages" the electoral commission to honor the will of the Zimbabwean people.
