GENEVA (Reuters) - U.S. officials will join talks in Geneva this month on forming a Syrian constitutional committee, U.N. Syria envoy Staffan de Mistura told reporters on Thursday, signalling movement in a process that had appeared at risk of stalling.

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De Mistura plans to meet senior Russian, Turkish and Iranian officials early next week and said he expected a similar meeting on June 25 with U.S., Saudi, British, French, German and Jordanian senior officials.

“We are seeing movement and we will keep seeking more of it,” de Mistura told reporters.

“I don’t expect – let’s be frank – major breakthrough, okay? But I am confident that progress is possible and there is something moving in that direction and we need to capitalise on it,”

De Mistura has a mandate from the U.N. Security Council to hold talks between Syrians on political reform, including writing a new constitution and holding elections.

But talks on those reforms, which are supposed to provide a political framework to end the seven-year war, have produced nothing and brought the warring sides no closer together.

Much of the political impetus for the talks has come from Russia, one of the closest allies of Syrian President Bashar al-Assad, while the United States appeared to dial down its involvement in the Syrian political process for several years.

In January, a Syrian congress in the Russian resort of Sochi agreed to set up a constitutional committee, and de Mistura is tasked with selecting its membership, after getting nominations from interested parties.

Syria’s government submitted its list of 50 candidates last month.

De Mistura said he hoped to get similar input soon from the Syrian opposition, which was doing “serious work” on its own list.