He called on Darfur rebel groups to close ranks to make the next round of peace talks successful.
The two conflicting sides have agreed to upgrade the level of representation in the next round of peace talks due to be held soon in the Nigerian capital Abuja. Previous talks have failed to yield a major breakthrough.
Thousands of people have been killed and over 1 million displaced since Darfur rebels took up arms against the government, accusing it of neglecting the arid region.
The UN official also condemned rampant armed robbery of aid supplies in Darfur, saying such an act would threaten the distribution of aid to the needy in the region.