The question of who will carry the mantle of the main opposition party risks adding to tensions in the world's top cocoa producer, which has a history of election-related violence including a brief civil war after the 2010 presidential contest that killed about 3 000 people.

In an interview with Reuters in the commercial capital Abidjan, Billon, 60, blamed party officials for the handling of legal challenges to Thiam's candidacy and did not rule out the possibility of representing another party, though he said it was too early to make such a move.

"I am asking for the PDCI's support," he said.

"It's a shame that President Thiam was eliminated, but it was the result of the lack of preparation of certain party officials that led to his elimination. That's why you always have to have several strings to your bow, especially when you're in politics."

The electoral commission published its final list of candidates last week, excluding Thiam, who denounced the decision as a sign of the "abandonment of democracy".

Ivory Coast law states that candidates must be Ivorian citizens and cannot hold another nationality.

Thiam renounced his French citizenship in February in order to meet eligibility conditions for the election.

But a court in Ivory Coast ruled in April that Thiam should be removed from the electoral roll because he was a French national when he registered. Thiam told Reuters after that decision that he planned to fight on and run anyway.

TENSE HISTORY

The notion of Ivorian identity was at the heart of past violence in Ivory Coast, and some fear lingering questions over Thiam's nationality in the run-up to the vote risk pushing those tensions back to the surface.

Incumbent President Alassane Ouattara himself was barred from seeking the Presidency over what opponents said were his foreign origins before he finally won election in 2010.

Ouattara, 83, has not said whether he will run again this year.

Billon told Reuters that if elected he would endorse a law to lift restrictions on dual nationality.

"You have thousands of Ivorians who live abroad, who have made their lives abroad, and who end up having dual nationality," he said.

Billon also said he would trim the civil service, crack down on corruption, promote private sector investment and move more government offices to Yamoussoukro, the political capital.

He said it was time for Ouattara and other politicians of his generation to leave the scene.

"Ivory Coast will change. I think our elders have had their day," he said.

--Reuters--