KAMPALA, Nov 11 (Reuters) - As fresh fighting looms in South Sudan with the onset of the dry season, there is little chance of peace talks to end a war that has already killed tens of thousands of people and created Africa’s largest refugee crisis, diplomats and analysts said.

South Sudan’s December-to-May dry season usually intensifies clashes because travel is easier on the impoverished country’s unpaved roads, which turn to mud in the rains.

“It would be a miracle if they get anything done,” said Peter Biar Ajak, a civil society leader who consults with African and western diplomats on the country’s stop-start peace process.

South Sudan’s war began in late 2013 between soldiers of President Salva Kiir, an ethnic Dinka, and his former vice president, Riek Machar, a Nuer, devastating the country’s swampy northeast.

A third of the country’s 12 million-strong population has fled their homes amid persistent reports of gang rape and ethnic violence.

An East African bloc, IGAD, led two rounds of peace talks over two years, culminating in a brief power-sharing agreement signed by Kiir and Machar in 2015. But even as IGAD urges a new ceasefire, the warring parties are preparing for more fighting.

The government plans to deploy a new force to around oil fields in the northeast, while rebels told Reuters they had procured new weapons in September and are organising in the south.

“We’re long past the point where power-sharing is a viable solution in South Sudan, if it ever was,” said Payton Knopf, former head of a U.N. experts panel for South Sudan.

Kiir’s government has little reason to negotiate; it holds the military upper hand and captured Machar’s main base in the northeast this year.

The rebels are disorganized: Machar is under house arrest in South Africa and his subordinates are scattered across six countries.

Complicating matters, many new groups have cropped up over the last 18 months and want to participate in peace talks.

Four parties signed the 2015 deal. This time, IGAD has named more than 20.

“This is where the test is now,” said Alex Rondos, the EU’s Special Representative to the Horn of Africa. “Can IGAD begin to exert a degree of united influence on all the parties to begin to find some degree of common ground?”

IGAD lost some credibility when a U.N. experts panel in September accused rival countries in the bloc of pursuing their own, conflicting interests. The South Sudanese government is also part of IGAD.

“IGAD is not speaking with one voice,” said Rebecca Garang, a prominent opposition-aligned figure. “President Salva is part of the IGAD even when he is part of the conflict.” (Editing by Katharine Houreld and Robin Pomeroy)