Updated

The United Nations envoy to Syria is working round the clock in a bid to secure a modest victory in the fourth round of talks held in Geneva.

Staffan de Mistura is due for another round of meetings Thursday marking a week of bilateral talks with the government delegation and opposition groups.

A top Syrian opposition negotiator told journalists overnight Wednesday the "envoy is really keen to start a political process on the basis of a clear agenda."

Nasr al-Hariri said the talks would likely culminate in a closing ceremony Friday and the parties may be back in Geneva for further discussions in a few weeks.

Setting the agenda and strategy to guide discussions has proven difficult as the main conflicting parties dig in their heels over form and semantics.