Rival Syrian delegations on Wednesday (May 17th) weighed a UN proposal on mapping a way to a new constitution as a new round of peace talks in Geneva entered a second day, AFP reported.

The sixth round of UN-backed negotiations is the latest drive to bring a political solution to the conflict which has claimed more than 320,000 lives.

UN envoy Staffan de Mistura met twice on Tuesday with both the Syrian regime delegation and the opposition High Negotiations Committee (HNC), with meetings running late into the evening.

Opposition members said their meetings focused on the issue of thousands of detainees still held in Syrian jails as well as the drafting of a new constitution.

De Mistura presented the HNC with a document proposing a team of civil society activists and technocrats responsible for mapping a way forward to a draft constitution, two opposition sources said.

The "consultative" team would begin work immediately on "specific options for constitutional drafting", according to a copy of the proposal.

It would aim to "prevent a constitutional or legal vacuum at any point during the political transition process being negotiated".

But the HNC's Munzer Makhos said opposition figures had "many reservations" and were still discussing it.

"It will become clear on Wednesday. This paper was a surprise -- it was not expected in the first place," Makhos said.

Syrian regime officials did not respond to requests for comment, but a source close to their delegation confirmed they had received a copy of the document.