BEIRUT (AP) — The U.N.’s special envoy for Syria said Sunday he hopes the Syrian government and the opposition will work with "a sense of seriousness and purpose” during the seventh round of talks this week over draft constitutional reforms.

Geir Pedersen spoke ahead of the talks that are scheduled to last until Friday in Geneva. The delegations are to focus on four topics including basics of governance, state identity, state symbols and the structure and functions of public authorities.

The talks that began more than two years ago were last held in October when Pedersen said the Syrian government’s refusal to negotiate on revisions to the country’s constitution was a key reason for their failure.

Syria’s conflict that began 11 years ago has killed a half million people and displaced half the country’s pre-war population of 23 million, including more than 5 million refugees. Though fighting has subsided over the past two years, there are still pockets controlled by the Syrian opposition, where millions of people live.

“Syria remains one of the gravest crises in the world and there is a clear need for progress toward a political solution,” Pedersen told reporters.

Pedersen said that earlier Sunday he met with the heads of the government and the opposition delegations and hopes those visits will clear obstacles to progress during the week.

A 2012 U.N. road map to peace in Syria approved by representatives of the United Nations, Arab League, European Union, Turkey and all five permanent Security Council members calls for the drafting of a new constitution. It ends with U.N.-supervised elections with all Syrians, including members of the diaspora, eligible to participate. A Security Council resolution adopted in December 2015 unanimously endorsed the road map.

At a Russia-hosted Syrian peace conference in January 2018, an agreement was reached to form a 150-member committee to draft a new constitution. A smaller, 45-member body would do the actual drafting, including 15 members each from the government, opposition and civil society. It took until September 2019 for the committee to be formed.