UN Syria envoy Staffan de Mistura said Sunday (February 26th) that several more rounds of Syrian peace talks will be needed to reach any accord, setting out three key discussion areas, AFP reported.

In a paper given to both sides, de Mistura said that by the end of the current session "we would have a deeper shared understanding of how we can proceed in future rounds" in each discussion area.

Syrian regime and opposition negotiators are in Geneva for a fourth round of UN-sponsored talks, but have been overshadowed by attacks on the ground.

The talks could last until March 5th, a few days longer than originally scheduled, according to an opposition source. The first full day of talks was Friday.

The main Syrian opposition group at the talks on Sunday accused the regime of "stalling", after the regime's chief envoy demanded all sides condemn a deadly Saturday suicide assault in Homs.

The High Negotiations Committee (HNC) made the charge after the Syrian regime's chief negotiator Bashar al-Jaafari said any opposition delegates who refused to condemn the attack were "accomplices of terrorism".

De Mistura identified the three "baskets" of issues to be discussed as governance, constitution and elections.

"I have asked you to be ready to engage in a continuous and inclusive process over the weeks and months ahead. If we are to succeed, we will need several rounds of talks, obviously," he wrote.

So far there have been no face-to-face talks between the two sides, with the UN envoy meeting each delegation separately, as in the three previous rounds.

Nevertheless, "I shall remain open throughout bilateral sessions during these initial talks to all possibilities for direct engagement and negotiations between the sides", de Mistura wrote.

He also set out a series of "ground rules" for the talks, including to "respect the others who are present in these proceedings".

He said he plans to spend an initial day bilaterally on each of the three main areas, followed by another day on each issue.

"It is clear that any progress on any basket is welcome. It is equally clear that nothing is agreed until everything is agreed," he said. "I would hope that by the end of this round we would have a deeper shared understanding of how we can proceed in future rounds in discussing each issue basket."