Geneva, Dec 17, 2018 (AFP)

The outgoing UN envoy for Syria will meet top diplomats from Iran, Russia and Turkey this week, his office said Monday, in a final bid to make headway towards a new Syrian constitution.

The talks scheduled for Tuesday in Geneva will likely be one of Staffan de Mistura's last meetings with major players in the Syrian conflict, as the veteran UN diplomat is due to step down in the coming days.

Russian foreign minister Sergei Lavrov will attend, a spokesperson from his office said.

A Turkish diplomatic source told AFP that Ankara's top envoy Mevlut Cavusoglu will be in Geneva along with Iranian foreign minister Mohammad Javad Zarif.

The UN did not immediately confirm the list of attendees.

The planned constitutional committee was agreed at a Russia-hosted conference in January.

The centrepiece of UN peace efforts in Syria, the committee would be tasked with negotiating a new post-war constitution that would pave the way to elections aimed at turning the page on seven years of devastating war.

But it has run into objections from the Syrian government.

The opposition has pushed for an entirely new constitution, but Damascus has said it will only discuss altering the current one.

In October, Damascus rejected a list presented by de Mistura of 50 civil society representatives and technical experts.