Mr Mugabe (l) and Mr Tsvangirai were said to be unable to agree
South African President Thabo Mbeki has denied a power sharing deal has been signed in Zimbabwe.
Ruling party officials had earlier said President Robert Mugabe had signed a deal with breakaway opposition leader Arthur Mutambara.
The deal would not have included Movement for Democratic Change (MDC) leader Morgan Tsvangirai, they said.
But Mr Mbeki, who is mediating, moved to stem rumours and said no party had signed any deal.
He was speaking after Mr Tsvangirai left the negotiations early on Tuesday.
Mr Mbeki said Mr Tsvangirai had simply left to reflect on the deliberations, the BBC's Karen Allen says.
Mr Mbeki said progress had been made and he felt a settlement could be reached.
Central to these talks is how much President Mugabe is prepared to relinquish power after 28 years at the top, our correspondent says.
Mr Mbeki's role is expected to come under scrutiny at a meeting of regional powers this weekend.
Welshman Ncube, the secretary general of the smaller opposition group led by Mr Mutambara, later confirmed no deal had been signed.
Mr Mugabe and Mr Tsvangirai were earlier reported to be unable to agree on how to divide power.
Our correspondent says a deal between Mr Mugabe and Mr Mutambara could be used to exert pressure and draw concessions from Mr Tsvangirai.
Mr Mbeki has been mediating between the ruling party and opposition
MDC Secretary General Tendai Biti said earlier: "The talks have not collapsed. It's just a time out."
Tuesday's talks followed a five-hour meeting on Monday and a marathon session on Sunday that lasted more than 13 hours.
Mr Tsvangirai won the first round of Zimbabwe's presidential election in March, before pulling out of a June run-off because he said there was a campaign of violence against his supporters.
The violence claimed the lives of more than 100 people and displaced hundreds of thousands.
Zanu-PF has blamed the opposition for post-election violence.
Correspondents say the Joint Operations Command (Joc) - a committee of Mr Mugabe's military chiefs - is believed to have masterminded Mr Mugabe's re-election campaign.
On Tuesday, Human Rights Watch said the campaign of violence had continued since the elections, with ruling Zanu-PF supporters continuing to terrorise villagers in rural areas.
The government was making little effort to dismantle torture camps set up by its supporters, and hundreds of opposition activists were still in hiding, it said.
At an Armed Forces Day event on Tuesday, Mr Mugabe praised his country's security forces for defending Zimbabwe's "hard-won independence".
"These sterling achievements have overcome numerous concerted efforts from some sections of the international community to destabilise our peace and stability and thus cause confusion in our country," he said.
He honoured George Chiweshe, head of the Zimbabwe Election Commission (ZEC), who has been criticised for his handling of the country's recent polls.