ANTANANARIVO (Reuters) - Madagascar's leader has vowed to disband his internationally rejected government and form an interim body with an ousted opposition leader following an ultimatum from the army to solve a festering crisis.

Analysts say there has been growing unease in some quarters of the government and military, and increased international pressure on Andry Rajoelina to solve the crisis, which has unnerved investors in the island's oil and mineral resources.

Rajoelina said that he was willing to meet with former President Marc Ravalomanana -- whom the former disc jockey ousted from power with the army's help -- but any deal would not be based on a previous pact brokered in Ethiopia and Mozambique.

"We are going to organise (elections) within three months, or three and a half months at the latest. There is no question of coming back to the Maputo and Addis Ababa accords, but to find out what can be the minimum acceptable to everyone," Rajoelina said on state television late on Wednesday.

"The current government will be dissolved and a new one will be formed ... The Government of National Union will be put in place after a meeting (between Rajoelina and Ravalomanana) which is expected to take place in South Africa."

Rajoelina has repeatedly set election deadlines and missed.

The crisis -- which began last March after weeks of violent protests, triggering a year of leadership squabbles on the world's fourth largest island -- has paralysed economic growth, slashed public spending and pushed up urban unemployment.

A power-sharing deal between Rajoelina, Ravalomanana and two other former presidents were signed last year, but persistent wrangling over who should get the top posts meant the accord was never implemented.

"This meeting (between Rajoelina and Ravalomanana) is the last chance," Rajoelina said.

But exiled former leader Ravalomanana told his supporters from South Africa that the only way forward was to implement the deals reached in Addis Ababa and Maputo.

"Do not think of any meeting if it is not about implementing the Maputo and Addis Ababa accords. These are criticised even though they have not been put in place."

Army chief General Andre Ndriarijoana -- who backed Rajoelina in taking power last year -- and other army bosses have given Rajoelina until the end of April to offer an acceptable way out of the political crisis.

The army did not say what action it would take if Rajoelina failed, but a military takeover cannot be ruled out.

But military arm-twisting will only succeed if the opposition leaders, including Ravalomanana, play their part.