Syrian Kurdish forces said to capture most of rebel-held former military airport

U.S. Foreign Secretary John Kerry and Russian Foreign Minister Sergei Lavrov (L) gesture before their bilateral talks in Munich, Germany, February 11, 2016, ahead of the International Syria Support Group (ISSG) meeting. REUTERS/Michael Dalder

MUNICH (Reuters) - Major powers began a new round of Syria talks on Thursday focusing on calls for a ceasefire and access for aid, but the mood was dour with Moscow showing no sign of calling off its bombing in support of a massive new government advance.

Russian Prime Minister Dmitry Medvedev raised the spectre of an interminable conflict or even a world war if powers failed to negotiate an end to the fighting in Syria, which has killed 250,000 people, caused a refugee crisis and empowered Islamic State militants.