The U.N. peace envoy for Syria Geir Pedersen said on Tuesday that an agreement could be reached on a committee to draft a new constitution for post-war Syria in the coming months as the Astana talks have helped lessen differences between warring sides.

The Norwegian diplomat, who took up the post in January from Staffan de Mistura, told the U.N. Security Council that the constitutional committee would be "a first sign of real movement" toward finding a permanent peace deal to an eight-year war that has killed more than 400,000 people and internally and externally displaced millions.

Discussions on the committee have been bogged down in disagreements over the composition of three lists of members from the government, opposition, civil society and religious groups. But after the latest Astana meeting last week in the Kazakh capital Nur-Sultan under Russia, Iran and Turkey and other discussions, Pedersen said he believed differences had been narrowed and that agreement was within reach.

The first meeting of the Astana process was held in Turkey in January 2017 to bring all warring parties in the Syrian conflict to the table to facilitate U.N.-sponsored peace talks in Geneva. The Astana talks support the establishment of a U.N.-backed constitutional committee in Syria to find a political solution. The planned constitutional committee, including representatives from the opposition, regime and guarantor countries, will be tasked with writing and establishing Syria's postwar constitution, which is seen as a stepping-stone to elections in the war-torn country. Asked whether the committee could hold its first meeting this summer, Pedersen told reporters: "Yes, I'm hopeful. I believe it should be possible to move forward. We have made tangible progress."

Meanwhile, the U.S. on Tuesday urged Russia to abide by its commitments and end the escalation in Syria's northwestern Idlib region amid continuous attacks causing casualties.

"The violence must end. The United States reiterates that any escalation in violence in northwest Syria will result in the destabilization of the region," State Department spokeswoman Morgan Ortagus said in a statement.

"We call on all parties, including Russia and the Syrian regime, to abide by their commitments to avoid large-scale military offensives, return to a de-escalation of violence in the area, and allow for unhindered humanitarian access to address the humanitarian disaster created by the ongoing violence," she added.

Anadolu Agency (AA) reported that three civilians have been killed in intensive airstrikes by the Syrian regime and Russia in the northern part of the Idlib de-escalation zone. During yesterday's attacks, three civilians were killed according to local sources.

In another attack on Monday, two civilians were killed in Idlib. The attack almost hit a Turkish observation point located in the Zawiya region, northwest of Hama, according to AA reporters on the ground.

On Saturday, Russian President Vladimir Putin said Russia has not ruled out a military offensive in Idlib, the last opposition stronghold, but considers it as "unnecessary" for the moment because of possible civilian casualties. "In principle, I do not rule this [offensive] out, but today together with our Syrian friends, we believe that this is inappropriate, given this humanitarian component," Putin said.

The civil war in Syria erupted in 2011 when the Assad regime harshly responded to protesters who had poured into the streets to demand more rights and freedom. The cruelty against the protesters triggered a rebellion in significant parts of the country, turning into a brutal civil war. According to U.N. figures more than 400,000 people have been killed, around 6 million people displaced internally and another 5 million driven abroad as refugees since the beginning of the civil war.