Former Madagascan president Marc Ravalomanana will return to the island nation on Saturday to help prepare for new elections nearly two years after his army-backed ouster.

The deposed president, who returns under the threat of arrest, declared himself as Madagascar's rightful leader on Thursday and said he is going back to start "desperately needed" talks that must pave the way to new polls.

"I am the democratically elected and constitutional president of Madagascar," he told a press conference in South Africa, where he has been in exile.

"I return to my country humbly, so that we can return to democracy, and together create a bright future for Madagascar."

The rule of his rival Andry Rajoelina, the army-backed opposition leader who ousted him in a coup in March 2009, was illegal and it was time for him to return home, he said.

"I am going back to start genuine dialogue, which is desperately needed," he said.

"Only a truly national consensus, forged by the Malagasy people, through direct talks in our own country, can restore us to democracy -- and can ensure that nobody can ever seize power illegally in Madagascar again," he said.

A Madagascan minister however warned Wednesday that Ravalomanana would be arrested if he returned.

He was sentenced in absentia to life in prison and hard labour last year for the death of 30 opposition protesters killed by presidential guards as they attempted to march on the presidential palace on February 7, 2009.

"I know the risks facing my return, but cannot allow them to get in the way of us restoring democracy. I have nothing to fear. I have done nothing wrong," he said.

"The regime is illegal. It cannot legitimate itself. This is similar to the apartheid regime," he said, referring to South Africa's decades of white minority rule.

Ravalomanana said he has informed South African authorities and will meet them on Thursday afternoon about his plan to return to Madagascar.

"I hope they will understand me and they will help my return to Madagascar," he said.

The exiled leader said he was prepared to listen and talk with anyone, and would call all partners and civil society to inclusive roundtable discussions.

"This must lead to a free and fair election.... It is time for me to come home" he said, adding that he would not oppose Rajoelina running in new polls.

"I intend to reach out to all Malagasy to build the consensus for peace."

Ravalomanana's sentencing last year was the third since his ouster. He was handed a four-year jail term and a fine for a case of conflict of interest in the purchase of a 60-million-dollar presidential jet and five years' hard labour over a land purchase.

Since he was toppled, the Indian Ocean island has been mired in a political crisis and efforts to resolve the impasse have floundered.

Last month, Southern African Development Community (SADC) mediator Leonardo Simao proposed a new plan to end the prolonged crisis, but none of the various parties have acted on it.

The plan proposes Rajoelina remain interim president and calls for the formation of an inclusive transitional government which would prepare for presidential and parliamentary polls to be held between May 1 and November 30 this year.

Ravalomanana rejected the proposal on Thursday.

"It is a pro-coup transition plan designed to keep me out of Madagascar and out of any political participation. It is unacceptable. It is undemocratic. It sets a bad example for Africa. It rewards a coup leader."

Rajoelina has rejected power-sharing deals with rivals and the international community has refused to recognise his rule.