An opposition faction controlled by South Sudan's first vice president has said it will join the country's ruling party.

Taban Deng Gai said on Monday that the political opposition Sudan People's Liberation Movement - In Opposition (SPLM-IO) had dissolved and joined the ranks of the SPLM party.

The vice president's announcement came before peace talks led by a regional bloc were scheduled to be held in neighbouring Ethiopia on May 17.

The move is expected to strengthen the position of the government of President Salva Kiir.

he SPLM fractured into different groups as a ruinous civil war erupted in December 2013 - two years after independence from Sudan - when forces loyal to Kiir started fighting those allied to his former deputy, Riek Machar. 

Previous attempts at peace have failed, with a ceasefire signed last December breaking down within hours and the most recent round of talks in February ending in deadlock.

Al Jazeera's Hiba Morgan, reporting from South Sudan's capital, Juba, said that despite the vice president's announcement, there will still many opposition groups "fighting the government".

"It makes it very hard to see how ... they can try to bring together the other factions of SPLM to join the current ruling party and try to end South Sudan's civil war," Morgan said.

"It could be a great step in trying to at least make reunification attractive to the rest of the parties by weakening them and making it seem like there is nothing to fight for if you have a stronger coalition in government."

SPLM-IO's decision came just a few days after an SPLM convention was held in Juba with the goal of reunifying the party.

It was the fourth of its kind in recent years.

"We must recognise that the SPLM is the glue that holds this country together," Kiir said at the convention.

"If we allow the SPLM to falter, history will never forgive us. Our unity as the SPLM family remains my priority."

SPLM was founded as the political wing of the Sudan People's Liberation Army which fought in the rebellion against the Sudanese government in 1983.  It represented South Sudan in an agreement signed in 2005 which paved the way for the country's independence six years later.

The war has killed tens of thousands of people and forced a quarter of the country's 12 million people from their homes. More than half of the population is in need of food aid according to the UN.