The visiting Chinese government's special representative for Darfur, Liu Guijin, has expressed his disappointment at Darfur's political process, which has been deadlocked since last October as Darfur's rebel groups have refused to return to the negotiating table.

"Unfortunately in the political process, no substantial progress has been made," Liu told a news conference Wednesday at the Chinese embassy in Khartoum at the end of a four-day visit in Sudan.

The political process is one side of a dual-track strategy which was initiated by China to end strife and violence and improve the humanitarian situation in Darfur. The other side of the strategy is the deployment of the UN-African Union hybrid peacekeeping force.

In a recent interview with Xinhua, Liu also said that no substantial progress has been made for several months in the political process, although on the whole some headway had been made in the peacekeeping operations despite difficulties. He urged Darfur rebel groups to return to the negotiating table.

This week marks the fifth anniversary of the outbreak of infighting among ethnic groups in Sudan's western region of Darfur, where rebels took up arms against the Sudanese government.

At the beginning, there were only two major rebel groups – the Sudan Liberation Movement (SLM) and the Justice and Equality Movement (JEM).

As conflicts continued, Darfur's rebels split into a confusing array of competing factions, which many analysts believe totaled at least 20 in number.

According to Liu, there were more or less five major rebel groups, namely, SLM-Minni Minnawi, SLM-Abdel Wahid el-Nur, SLM-Unity, JEM and the United Resistance Front (URF). Some leaders of these major factions are living in European capitals, according to media reports.