A United Nations plan to end the seven-year civil war in Syria has run aground after Damascus blocked the world body's proposal for a committee to draft a new constitution, provoking anger among western powers.

 

U.N. special envoy Staffan de Mistura has been working since January on forming a group of 150 members to thrash out a new constitution, seen as a first step to winding down a conflict that has cost more than 360,000 lives.

 

Under the U.N. plan, the Syrian regime would choose 50 of the committee members, the Syrian opposition another 50 and the U.N. would nominate the final 50, composed of representatives of civil society and technical experts.

 

De Mistura, a veteran Italian-Swedish diplomat due to step down next month, said Friday that Foreign Minister Walid Muallem rejected the last list of UN-proposed names and suggested his own method to the final 50 members during talks in Damascus this week.

 

"Walid Muallem didn't accept a role for the U.N. in identifying or selecting a third list," the envoy told the U.N. Security Council by video conference during an emergency session called by the United States.

 

"Rather, Mr Muallem indicated that the governments of Syria and Russia had agreed recently that the three Astana guarantors (Iran, Russia and Turkey) and the Syrian government would in consultations among them prepare a proposal as regards the third list."

 

De Mistura said withdrawing the U.N. list was only possible "if there was an agreement on a new credible, balanced and inclusive list" that complied with U.N. resolutions and commitments made in January talks in the Russian resort town of Sochi.

 

- 'Unacceptable' for Washington -

 

Unsurprisingly, the Syrian counter-proposal was met with widespread condemnation from western powers, led by Britain, France and the United States.

 

"The United Nations has exclusive control over the committee's membership, schedule and scope of work -- as affirmed by the Russian Federation in its January 2018 Sochi Declaration," said Jonathan Cohen, the deputy U.S. ambassador to the world body.

 

"Further obstruction on the committee's formation is unacceptable," he added, calling for urgent action.

 

French ambassador Francois Delattre warned that "the risk of new escalation cannot be ruled out. That can only be done through a solution that is politically credible and inclusive."

 

"It is right that the U.N. is involved," in the political process, said Karen Pierce, the British ambassador to the U.N., stressing the world body's deep engagement with issues of humanitarian aid, refugees and health.

 

Vassily Nebenzia, the ambassador of Russia, a key ally of the Syrian regime, was critical of the decision to hold the Security Council meeting.

 

"We cannot go against the will of Syria," he said.

 

"We will help Staffan de Mistura create this constitutional committee with respect for Syrian sovereignty."

 

Nebenzia urged caution in the process and stressed that the outgoing diplomat, who already addressed the council last week, not make the issue his "political legacy."

 

De Mistura said he would take part Saturday in a special summit in Istanbul bringing together leaders from France, Germany, Russia and Turkey.

 

The Syrian summit will be followed on Monday by a meeting of the so-called "small group" of Britain, Egypt, France, Germany, Jordan, Saudi Arabia and the United States, a U.N. official said.

 

De Mistura will then go on to Geneva to meet with the Astana accord guarantors Iran and Russia, which are backing the regime of President Bashar al-Assad, and Turkey, a major sponsor of anti-regime rebel groups.

 

The U.N.'s attempt to broker peace in Syria have largely been eclipsed by a parallel diplomatic initiative by Moscow, Tehran and Turkey.