Qatar's foreign minister has said that "de-escalation zones" are not a substitute for political transition in Syria, adding that President Bashar al-Assad ought to leave office in any final peace agreement.
Speaking to Al Jazeera in Washington, DC, Mohammed bin Abdulrahman Al Thani said the de-escalation zones "are a step towards reaching a solution and not the solution itself".
"There should be a clear message that political transition is based on the Geneva I declaration, which ends with Bashar al-Assad and his regime leaving power and the establishment of a transitional authority," Al Thani said.
Staffan de Mistura, the UN special envoy to Syria, has said talks between the Syrian government and opposition on ending the war are to reconvene in Geneva on May 16.
De Mistura says he hopes that an agreement reached in Astana last week between Russia, Iran and Turkey to set up the so-called de-escalation zones will be fully implemented.
On Monday, Walid al-Moualem, Syria's foreign minister, said there would be no role for the UN or other "international forces" in the de-escalation zones but that Russia saw an observer role for military police.
He gave no further details.
"We do not accept a role for the United Nations or international forces to monitor the agreement," he said.
Russia said on Monday that it had tabled a draft UN Security Council resolution backing the de-escalation zone deal.
A source at the UN told Russia's Interfax news agency that "a vote on the draft will take place possibly this week".
Russia and regional power Iran have helped President Bashar al-Assad gain the military advantage against rebels fighting for six years to unseat him.
Russia has led most of the recent diplomatic efforts to end the conflict.