Robert and Grace Mugabe: What next for Zimbabwe?

Zimbabwe's ruling Zanu-PF party is planning to support impeachment proceedings against Robert Mugabe, after he ignored a deadline to stand down as president.

Zimbabweans - and many watching around the world - were astounded on Sunday night when Mr Mugabe addressed the nation and said that far from stepping down, he was going to stay on and preside over the ruling party's congress in December.

So with Mr Mugabe defiant, and the army insisting that it has not carried out a a coup, what are the options for getting him to vacate his position?

Here are five possible scenarios:

Zanu-PF says it will launch impeachment proceedings against Mr Mugabe when parliament convenes on Tuesday.

Impeachment is the process of removing a president via parliament.

Both the National Assembly and the Senate can begin proceedings to remove the president if both pass simple majority votes against him.

A two-thirds majority is needed in both houses in order for impeachment to succeed.

Zanu-PF has a two-thirds majority in the House of Assembly, but not the Senate.

The formal process is expected to start on Tuesday but it is not clear how long it would take.

The benefit of this process for the military is that it allows the generals to say the removal of the president was done in accordance with the constitution, in keeping with their statement that this is not a coup.

The downside for them is that it does not guarantee that the man widely thought to be their favourite for president will get the top job straight away.

Emmerson Mnangagwa, whose sacking prompted the military's action, could not immediately take over from Mr Mugabe, because constitutionally it is the current vice-president who should fill the vacancy.

At the moment that person is Phelekezela Mphoko - a man whose sympathies are known to lie with Grace Mugabe, and who was expelled by Zanu-PF on Sunday.

Whether the army can persuade Mr Mugabe to appoint their preferred candidate as vice-president before stepping down remains to be seen.

Some analysts have argued that this may be what the generals were discussing with him - and it may also be his trump card.

But given how difficult it has been to get Mr Mugabe to step down, the chances of getting him to concede further ground look increasingly slim.

President Mugabe was defiant when he made his televised address on Sunday.

Despite having been sacked by Zanu-PF, he said "the party congress is due in a few weeks and I will preside over its processes".

He suggested that he was willing to forgive the military action, and said "whatever the pros and cons of how they [the army] went about their operation, I, as commander-in-chief, do acknowledge their concerns".

It had been reported that Mr Mugabe had agreed to resign.

It is unclear whether he changed his mind, or if these reports were incorrect. But BBC Africa editor Fergal Keane says it makes the military look weak.

Some suggest that there may be grounds within Zanu-PF's own rules which might allow Mr Mugabe to reject his sacking by the party.

President Mugabe is known for both being shrewd and stubborn. So he may well have another ace up his sleeve.

Initially it had been thought that the military was trying to reach a deal which would allow President Mugabe to stay in Zimbabwe once he had stood down.

But the current stalemate makes that look less likely.

From the point of view of Mr Mugabe, and his wife, there is a fear that even if he were to be promised immunity from prosecution now, that could be removed by a future government.

So it might mean that Mr Mugabe is forced into exile.

Until recently, neighbouring South Africa would have been a natural place for him to go.

Mr Mugabe enjoys a high level of respect there, in large part because of his support for the fight against apartheid rule.

Indeed, the opposition EFF party has called on the government to "prepare to welcome President Mugabe for political asylum".

The Mugabes are reported to have a number of properties in South Africa.

The sticking point would be what happens to Grace.

She was granted diplomatic immunity after allegedly assaulting a model in a hotel room in Johannesburg in August.

But model Gabriella Engels is trying to get the diplomatic immunity order set aside. If successful, it would mean Mrs Mugabe could face prosecution should she go to South Africa.

So if not South Africa, then where?

Other possible options are Singapore and Malaysia, where the Mugabes also have properties.

The leader of the opposition Movement for Democratic Change-Tsvangirai (MDC-T) party is back in Harare after receiving treatment for cancer in South Africa, fuelling speculation about negotiations for a unity government.

This is the scenario that many in the West, and of course the opposition, would prefer.

Another opposition leader, Tendai Biti, has said that he would join a national unity government if Mr Tsvangirai was also in it.

But the military takeover was not a change of regime. It was an internal dispute within Zanu-PF, and that party is still very much in power.

The military is to a large extent the armed wing of Zanu-PF.

And the man it supports as leader - Emmerson Mnangagwa - helped Robert Mugabe carry out some of his most controversial policies.

He is also, some say, more ruthless.

So it is far from clear that the ousting of Mr Mugabe would improve the lives of ordinary Zimbabweans.