The United Nations will host a new round of peace talks on Syria next week in Vienna, a UN statement said Wednesday, just days before Russia opens a conference on ending the war.

The January 25-26 talks will be followed by a peace congress in Russia's Black Sea resort of Sochi on January 29 and 30 aimed at finding a settlement to the nearly seven-year war.

The UN said that special envoy Staffan de Mistura "expects that delegations will be coming to Vienna prepared for substantive engagement with him."

It added that "any political initiative by international actors should be assessed by its ability to contribute to and support the United Nations-facilitated Geneva political process and the full implementation of resolution 2254," a roadmap for ending the conflict set out in 2015.

Syria's six-year war has claimed more than 340,000 lives, forced millions to flee their homes and left Syria in ruins.