Jan Pronk said on Friday that the two main rebel groups and the Sudanese government, which started a seventh round of talks in Abuja, Nigeria, this week, remain distant on many issues on the negotiating table - including sharing power and oil wealth.
But he said: "We are going in the right direction. It is possible that there is a peace agreement at the end of this year, like last year on the 31st of December we had peace between the north and the south."
Pronk, a former Dutch environment minister and a Sudan veteran, was referring to an accord nearly a year ago ending a separate 20-year conflict.
A "framework agreement" for Darfur was "possible but difficult because the positions of the parties in the talks are still far apart", he said.
AU troops in Sudan may increase
from 8000 to 12,000
Among the reasons for his guarded optimism was that after the peace deal between the north and south, Sudan's National Unity government has included the Sudan People's Liberation Movement, creating a "different political climate".
The former rebel movement from the south is "more sympathetic to the demands of liberation movements in Darfur", according to Pronk.
However, the possibility of independence - envisioned in south Sudan where a referendum on secession is due within six years of the peace deal - was "not in the cards" for Darfur.
Pronk, noting that Sudan was due to celebrate its 50th year of independence on 1 January, said that the Khartoum government had an interest in making peace by that symbolic anniversary.
"Quite a lot of political leaders in Sudan would like to show that Sudan can be not only independent but also peaceful," he said.
With peace, the number of African Union (AU) troops in Darfur must be raised to at least 12,000 from fewer than 8000 now, as people "don't trust their own government" after so much violence by Arab Janjaweed militias and bandits, he said.
"Quite a lot of political leaders in Sudan would like to show that Sudan can be not only independent but also peaceful"
UN envoy in Sudan
The militias stand accused of a widespread campaign of rape, killing and burning in non-Arab villages during the two-and-a-half-year revolt, which has forced more than 2 million people from their homes and caused a massive humanitarian crisis.
"The peace agreement is only at a rather shallow, superficial level of the whole conflict, but we need peace to be able to start such talks throughout Darfur," Pronk said.