* More than 1,000 people killed in three weeks of fighting
* China is top investor in South Sudan's oil industry
* Sudan's Bashir visits Juba, urges end to fighting
China, the biggest investor in South Sudan's oil industry, called for an immediate ceasefire in the world's newest state on Monday as rebel and government negotiators haggled over the scope of peace talks meant to end three weeks of fighting.
Chinese Foreign Minister Wang Yi said Beijing was deeply concerned by the unrest in South Sudan, which has killed more than a thousand people and forced the government to cut oil production by about a fifth.
"China's position with regards to the current situation in South Sudan is very clear," Wang told reporters in Addis Ababa, where the peace talks are taking place. "First, we call for an immediate cessation of hostilities and violence."
An Ethiopian delegate said Wang also met both rebel and government delegations.
China, Wang said, would do what it could to help restore stability in South Sudan and urged international powers to back the Ethiopian-led mediation efforts.
Three weeks of fighting, which began in the capital but spread beyond, often along ethnic faultlines, have pitted President Salva Kiir's SPLA government forces against rebels loyal to former vice president Riek Machar.
The peace talks opened formally on Saturday in Ethiopia but delegates have yet to sit down for face-to-face negotiations.
A member of the rebel camp in Addis Ababa told Reuters the government delegation would only a discuss a ceasefire and not the release of political detainees allied to Machar.
"For us, that is a priority. It's at the very top of our agenda," said the rebel delegate who withheld his name.
The United States and the European Union have backed the rebels' call for the detainees to be released. South Sudan refuses, saying they are accused of a capital offence.
The stuttering talks have unnerved international powers who worry South Sudan could spiral into full-blown civil war.
"The delay tactics that we are seeing at the moment in Addis Ababa give us cause to fear that the conflicting sides have no real interest in a swift political solution," said a German Foreign Ministry spokesman.
The fighting is the worst in South Sudan since it won independence from Sudan in 2011 in a peace deal that ended one of Africa's longest civil wars.
Relations between the two countries have stabilised since the civil war foes came close to conflict again in disputes over oil fees and the border in the early part of 2012.
On Monday, Sudanese President Omar al-Bashir, who has said little on the unrest in South Sudan, met Kiir in Juba for the first time since the fighting erupted.
"No solution can be reached through violence. All warring parties must sit down and settle the conflict politically," Bashir told a news conference in Juba.
South Sudan's oil is a shared interest of China and Sudan. Oil giant BP estimates South Sudan, a country the size of France, holds Sub Saharan Africa's third largest reserves.
China is already the biggest investor in oilfields in South Sudan, through state-owned Chinese oil giants China National Petroleum Corp (CNPC) and Sinopec. The fighting forced CNPC to evacuate workers.
All of landlocked South Sudan's oil is piped through its northern neighbour, providing vital hard currency in transit fees for Khartoum.
Asked what Bashir's motive would be for visiting Juba, South Sudan expert Douglas Johnson said: "One is certainly the lost oil revenues. "No oil company will return to the oil fields while they are contested."
South Sudan's oil production fell by 45,000 barrels per day to 200,000 bpd after oilfields in its northern Unity state were shut down due to fighting.