The power struggle has brought weeks of riots, protests and looting
President Marc Ravalomanana of Madagascar has defied an ultimatum to resign in the face of a mass opposition rally in the capital, Antananarivo.
After the deadline passed, he emerged from the presidential palace, which is defended by hundreds of his supporters, to say he had no plans to resign.
Opposition leader Andry Rajoelina has threatened to lead a march on the palace if he does not leave.
At least 100 people have been killed since protests broke out in January.
The opposition, which is trying to set up its own government, has occupied the prime minister's offices.
An aide to Mr Rajoelina, who did not wish to be named, said after the deadline passed that the opposition was still waiting for the president to quit.
"If we don't receive the call [from the president to say he has resigned], something will happen," the aide told Reuters news agency.
The BBC's Jonah Fisher reports that the opposition do not seem to have the appetite for a violent confrontation with the president and his supporters and prefer, instead, to keep turning up the pressure.
Nor, our correspondent adds, has there been any indication that the opposition will settle for a coalition with Mr Ravalomanana.
Sticks and stones
Presidential supporters are manning barricades around the park where the presidential palace stands, some 12km (eight miles) from Antananarivo.
December 2006: Marc Ravalomanana returned as president for second term
31 January 2009: Opposition leader Andry Rajoelina says he is in charge of the country after weeks of bloody protests
3 February: Mr Rajoelina is sacked as mayor of Antananarivo
5 March: Mr Rajoelina goes into hiding
13 March: President Ravolamanana urges supporters to turn out and defend his authority
14 March: Mr Rajoelina re-emerges and gives president just hours to resign
Several big orange skips full of sand have been set up about 300m (yds) from the palace and hundreds of people have been walking around, holding large sticks, our correspondent reports.
Some people have got stones and the atmosphere is tense.
Everyone is waiting to see if the opposition do come to try and take the palace but this show of force seems to have called the opposition's bluff and there has been no sign of them moving in on the palace, our correspondent says.
"I'm still the president of Madagascar and I will remain the president," Mr Ravalomanana told the BBC.
"We must have a national conference and respect democracy."
Mr Ravalomanana, democratically elected to a second term in office in 2006, also issued a statement condemning the opposition which, he said, did not have "the power bestowed by democratic elections".
"This [opposition] movement is and remains a street protest which uses terror and repression to survive," he said.
"A self-proclamation does not equate to legitimate power."
Mr Rajoelina, a former mayor of the capital who was sacked by the government last month, rallied some 5,000 supporters clad in orange T-shirts and hats in central Antananarivo on Saturday.
"There is only one demand, that's the departure of Ravalomanana," he said.
But he ruled out using force against the president.
"I have clean hands," said the opposition leader, who accuses the president of being a tyrant who misspends public money.
"I have no intention of killing him [Mr Ravalomanana]. I have no intention of sending in tanks and soldiers."
Mr Rajoelina has been trying to establish an alternative cabinet with himself as president.
On Wednesday, the leader of a widening mutiny within the army ousted the chief of staff and a day later the military police said they would no longer take orders from the government.
The crisis has hurt the country's economy. Its tourist industry, worth nearly $400m (£290m) a year, has now had two months with no revenue.
Under President Ravalomanana, Madagascar's economy opened to foreign investment but 70% of the nation's 20 million population still live on incomes of less than $2 (£1.40) a day.
Fort Dauphin in the south-east of the island has remained calm and peaceful throughout the recent political turmoil. Remote and isolated, it lacks the infrastructure which has been destroyed in other regional centres. There are no furniture stores or supermarkets to loot here. The area is developing rapidly linked to recent mining investment, but there's still no decent road access to other regions. Rural communities in the region benefit from the efforts and donations of foreign volunteers working with NGOs and academic institutions. My advice to anyone thinking of coming to Madagascar is to seek information specific to the region they intend to visit...
Shirley Smith, currently in Fort Dauphin, Madagascar
For sure this is a very sad event for my country, but the worst thing for the Malagasy People is to recognize that we have no Army but traitors in front of us. Rasolofonirina Marcel, Antananarivo, Madagascar
As an employee in a subsidiary of a British exploration company, I feel really concerned about the behaviours of those dissidents troops. They do not really help in easing the mind of our investors as they provide support to the opposition leaders in unlawfully taking over the Ministries from the elected Government. We are obviously witnessing the unfolding of a coup. This should be made clear to all. A resolution should be voted at the level of the African Union to give mandate to the SADC Brigade to come and protect the legal President so as to ensure peaceful settlement to take place.
Rija, Antananarivo, Madagascar
Actually the majority of the Malagasy people support the President Ravalomanana. Although the former Mayor was at the beginning supported by a number of of very young people, most of them they gave up when they realised that he was going to put the country in a political crisis... We are all tired with his situation. We wonder why he didn't wait till the elections to get the power. Why he never told us about his political project for the future? The only thing he keeps on saying is that Ravalomnanana is a thief, so he should be the president of Madagascar. Very democratic! He doesn't even have a legal political party. Who does he represent? Malagasy are poor but not stupid. Helene, Antananarivo
I have been living in Madagascar since 2003. I am a Canadian consultant working on international donor financed projects. I live 100m from the Antananarivo town hall... The mayor's campaign has no foundation in law and the intellectual class find nothing of substance in his platform. The president may have made some mistakes in the past in listening to the opposition and he has apologized for this. But he has been lawfully elected without a doubt a couple of years ago. The mayor's campaign is simply a badly disguised attempt at a coup d'état. Unfortunately the economy has just been destroyed altogether and it will take 2-3 years to recover. Only the poor people of Madagascar will really suffer from this. Again. Roger Dhristen, Antananarivo, Madagascar
Are you in Madagascar? Are you affected by the issues in this story? Send us your comments and experiences using the form below.
Send your pictures to firstname.lastname@example.org or text them to +44 7725 100 100. If you have a large file you can upload here.
Read the terms and conditions
At no time should you endanger yourself or others, take any unnecessary risks or infringe any laws.
The BBC may edit your comments and not all emails will be published. Your comments may be published on any BBC media worldwide.