GENEVA (Reuters) - The United Nations Special Envoy for Syria said on Wednesday he had invited the Syrian government and opposition to a special meeting to be held next week in Vienna, Austria.

FILE PHOTO: U.N. special envoy on Syria Staffan de Mistura attends a meeting with Russian Foreign Minister Sergei Lavrov and Defence Minister Sergei Shoigu in Moscow, Russia December 21, 2017. REUTERS/Maxim Shemetov

Staffan de Mistura said the Jan. 25-26 meeting would focus on constitutional issues in Syria.

“The Special Envoy looks forward to the participation of both delegations in this special meeting,” De Mistura’s office said in a statement.

“He expects that delegations will be coming to Vienna prepared for substantive engagement with him and his team with a specific focus on the constitutional basket of the agenda towards the full implementation of Security Council resolution 2254,” the statement added.

That refers to a text agreed by major powers that calls for a new constitution, U.N.-supervised elections and transparent and accountable governance.

The date for the meeting puts it just ahead of Russia’s plan to hold a Syrian congress of national dialogue in the Black Sea resort of Sochi on Jan. 29-30.

It will also coincide with the World Economic Forum at Davos, where de Mistura will facilitate a special diplomatic session behind closed doors on Jan. 25.

De Mistura has presided over a series of Syrian talks in Geneva, with a mandate to discuss new elections, reformed governance, a new constitution and the fight against terrorism.

The warring sides never talked face-to-face, and it was only in the eighth round, in December, that the opposition united in one delegation, raising hopes of direct talks for the first time.

But the Syrian government delegation objected to the opposition’s tough line on the future of President Bashar al-Assad, and the talks achieved nothing.

Frustrated by the deadlock, de Mistura subsequently told the U.N. Security Council that he wanted to take the initiative, with the U.N. proposing a timeline for elections and offering guidance on constitutional reform, while bringing a broader section of Syrian society into the process.

A source close to the talks said de Mistura was still expected to talk to the two sides separately in Vienna.

Despite Assad’s sweeping gains on the battlefield, with strong Russian and Iranian support, the complex war has continued towards its seventh anniversary in March, with hundreds of thousands dead, about 400,000 people still under siege and no sign of an end to the violence.