South African government ministers are in Harare for crisis talks with ousted President Robert Mugabe and military leaders who have seized control.
They are trying to reach a deal on the future of the man who led the country for 37 years before being put under house arrest on Wednesday.
The Southern African Development Community (Sadc) regional bloc is to hold emergency talks shortly.
But sources suggest Mr Mugabe may be resisting pressure to resign.
They say Mr Mugabe is insisting he remains the legitimate president. Regional bodies such as Sadc and African Union (AU) will be keen to reach a constitutionally sound resolution to the crisis rather than to endorse a military takeover, say correspondents.
However, the power struggle over who might succeed him, between his wife Grace Mugabe and her rival former Vice-President Emmerson Mnangagwa, has split the ruling Zanu-PF party in recent months.
Last week, Mr Mugabe came down in favour of his wife, sacking Mr Mnangagwa, a veteran of Zimbabwe’s anti-colonial struggle and of Zanu-PF.
That proved too much for military leaders who seized control of the country on Wednesday.
Mr Mugabe has been under house arrest.