Liu Guijin, the special Chinese envoy on Darfur, also repeated calls for the Khartoum government to show more flexibility on "technical" issues still blocking the deployment of a joint U.N.-African Union peacekeeping force in the war-ravaged western Sudanese region.

Liu, whose country is a big investor in Sudan's oil industry and is its largest weapons supplier, reported no significant steps forward in political talks on Darfur.

"Unfortunately on the political process, no substantial progress has been made," Liu said in Khartoum after discussions with top Sudanese leaders, including President Omar Hassan al-Bashir.

Of the five key Darfur rebel groups, only two have agreed to unify their positions and join the peace talks, stalled since the failed summit in Libya in October.

The two key rebel factions, the Justice and Equality Movement, or JEM, -- the biggest military group -- and the populist Sudan Liberation Movement, or SLM, led by Abdel Wahed Mohamed el-Nur, were still putting conditions on attending any talks.

"We urge our Western friendly countries ... to use their positive influence to engage those factions who have until now resisted to come over to the negotiating table, to join the political process," Liu said.

Failing to launch a successful political process, he argued, means the joint AU-U.N. mission would not be "sustainable."

TROUBLE WITH TROOPS

Sudan has so far rejected the notion of accepting non-African contribution in the joint AU-U.N. force of 26,000 troops until all African soldiers have deployed in Darfur.

Liu said Khartoum had not "closed the door regarding accepting non-African countries."

International experts estimate some 200,000 have died and 2.5 million have been forced to flee their homes since the conflict flared in 2003 when rebels took up arms against the central government, accusing it of neglecting the region.

The United States calls the violence a genocide. Sudan rejects this and says only 9,000 people have lost their lives.

"We appeal to China to stop supplying the Khartoum government with arms," SLM rebel leader Nur said.

"We want security on the ground first. There should be conflict suspension before addressing the root causes of the problem," he told Reuters by telephone from France.

China's role in Sudan has come under new scrutiny since film director Steven Spielberg quit as an artistic director to the 2008 Beijing Olympic games, saying China had failed to use its influence in Khartoum to seek peace in Darfur.

Separately, New York-based rights watchdog Human Rights Watch criticized the U.N. Security Council -- of which China is a veto-wielding member along with Russia, the United States, Britain and France -- for keeping about what it said were Khartoum's recent attacks on civilian villages in West Darfur.

The group said in a statement that the council's inaction has given Sudan a green light to continue attacking civilian targets, flouting international law and council resolutions.

"The Sudanese government's recent attacks take us back to the very darkest days of the conflict," said Georgette Gagnon, Africa director at the organization. "The Security Council shouldn't stand by as though this is 'business as usual.'"