LUANDA, August 6, 2008 (AFP) - Angola's main opposition on Wednesday received backing from a party seen as popular among young voters ahead of the country's first elections since the end of a 27-year civil war.

The main faction of the Party for Development and Progress of Angola (PADEPA) -- a newcomer since the last elections in 1992 which has gained popularity among the youth -- said it would support UNITA's election campaign.

'All militants, sympathisers and friends of PADEPA will support UNITA in this election,' leader Carlos Leitao told reporters.

UNITA spokesman Adalberto da Costa Junior called it 'very important support.'

The decision to back UNITA comes after the faction, regarded as the true PADEPA, lost out on the chance to take part in the September 5 elections.

Angola's Constitutional Court instead recognised the party's smaller faction in what was widely seen as a political decision.

PADEPA, which split earlier this year, formed in the ruling party stronghold of Cazenga, the most populous area of the capital Luanda with one million people, and quickly galvanised the youth.

It was the first party to challenge the government's ban on political rallies and marches after the end of the civil war in 2002, a move that resulted in police detaining much of its leadership.

President Jose Eduardo dos Santos earlier this week pledged polls would now be held every four years in accordance with constitutional rules introduced for the last 1992 elections.

The Angolan leader, who state news agency ANGOP reported left the country on Wednesday to attend the Olympics opening ceremony in China, also called for 'respect and tolerance' ahead of the vote.