Syria's U.N. ambassador on Thursday urged Western powers to lift crippling economic sanctions against the war-torn country if they are serious about helping millions of Syrian refugees to return to their homeland.

Bashar Ja'afari spoke in the Kazakh capital of Astana where Russia, Turkey and Iran are holding talks with the Syrian government and the opposition. The mediators are speaking separately to the warring sides, which are not meeting face-to-face.

Nearly 6 million Syrians have fled the civil war, now in its eighth year, to neighboring countries and Europe. Syria and Russia, one of its main backers, insist that the refugees can safety return home now while many Syrians fear that they will face persecution.

Ja'afari says lifting the sanctions imposed on Syria would be "the real test" for the West.

"Sanctions should be lifted so that people could return to their jobs, return to a normal life, to the development and flourishing of their country," he said in comments carried by Russian news agencies.

Europe says it will keep its sanctions in place as long as "repression" continues in Syria, extending the measures to 2019.

U.N. Special Envoy for Syria Staffan de Mistura in a statement after the talks expressed his disappointment with the fact that the warring sides and the mediators still have not agreed on what should be included in the committee meant to draft a new constitution for the country.

De Mistura said he "deeply regrets" that the Astana meeting did not show any tangible progress in that direction and called the meeting "a missed opportunity to accelerate the establishment of a credible, balanced and inclusive, Syrian-owned, Syrian-led, U.N.-facilitated constitutional committee."

Russian envoy for Syria Alexander Lavrentyev told Russian news agencies after the meeting that Russia would love to see the committee formed "as soon as possible" but said the work to form the committee may stretch into next year.

Ja'afari said that all foreign "illegitimate" forces should pull out of the country if the intention is to help Syria come out of the crisis. He named the U.S., Turkish, French and British forces only. He estimated that more than 10,000 Turkish soldiers are in northern Syria.

In apparent reaction to Ja'afari's remarks, Ahmed Tumah, Syrian opposition representative in Astana who heads the opposition-led Turkey-backed government which operates in the areas currently under the control of the Free Syrian Army, said the return of refugees should be arranged only after there is a political solution in place.

"Our problem with the regime is political," he said. "The regime doesn't want to take any step on the political level, only militarily."