The ruling Zanu-PF party will discuss the impeachment process on Monday, its chief whip said, after a noon (10am GMT) deadline expired for the 93-year-old to end his nearly four decades in power.
The deadline passed as reports suggested Mr Mugabe has agreed to stand down after he avoided any mention of resignation in a rambling national address on Sunday night.
A resignation letter has now been drafted, CNN said, citing sources familiar with his negotiations with the generals who seized power in Harare last week. Under the terms of the deal, Mr Mugabe and his wife Grace would be granted full immunity, CNN said.
Pressure was now mounting from all sides on the 93-year-old, the only leader Zimbabwe has known since its independence in 1980, to swiftly end the confusion that has gripped the country since the de facto coup last Wednesday.
Mr Mugabe stunned Zimbabweans in a rambling late night Sunday television address by avoiding any mention of resignation, pledging instead to preside over a congress next month of ZANU-PF, which had sacked him as its leader only hours earlier.
Moments after Mr Mugabe’s address, war veterans’ leader Chris Mutsvangwa told Reuters they would lead public protests in the streets of Harare.
Mr Mugabe was also given a deadline of noon (10am GMT) on Monday to stand down or the ruling Zanu-PF will begin impeachment proceedings against him.
Parliament does not sit on Mondays so any impeachment would have to wait until Tuesday, although a vote may not necessarily take place the same day.
Zanu-PF chief whip Lovemore Matuke told Reuters on Monday that the party’s members of parliament would meet at 12.30pm GMT to start mapping out Mugabe’s impeachment.
Two senior government sources told Reuters late on Sunday that Mugabe had agreed to resign but did not know details of his departure.
There has been speculation that he read the wrong speech in his live television address on Sunday or skipped over passages about standing down.
Zanu-PF’s central committee had earlier named Emmerson Mnangagwa as its new leader.
It was Mr Mugabe’s sacking of Mr Mnangagwa as his vice-president – paving the way for his wife Grace to succeed him – that triggered the army to seize control.
On Saturday, hundreds of thousands took to the streets of Harare to celebrate Mr Mugabe’s expected downfall and hail a new era for their country.
On Monday Theresa May said it was clear that Mr Mugabe had lost the support of the Zimbabwean people.
“We would say that while the situation remains uncertain, we would appeal for everyone to refrain from violence,” the prime minister’s spokesman said. “We hope to see a peaceful and swift resolution to the situation.”
The huge crowds in Harare have given a quasi-democratic veneer to the army’s intervention, backing its assertion that it was merely effecting a constitutional transfer of power, rather than a plain coup, which would risk a diplomatic backlash.
Armoured vehicles manned by soldiers were still stationed on some street corners in the capital on Monday.
Zambian President Edgar Lungu has sent former president Kenneth Kaunda to Harare to try to convince Mr Mugabe to step down in a “dignified exit”. “Dr Kaunda used the presidential jet and has already arrived in Harare,” a senior government source told Reuters