Syria claims it remains committed to destroying its chemical weapons arsenal by the middle of this year despite missing another deadline.
The delay is being blamed on the war with anti-regime militants and flouts an agreement brokered last September to avert an United States' air strike, mooted after a chemical attack in east Damascus that killed hundreds and drew global outrage.
Less than 5 per cent of Syria's chemical arsenal, thought to total more than 1,300 tonnes, has been shipped out for destruction. By Wednesday, more than 90 per cent should have been surrendered under a pact with the UN and the Organisation for the Prohibition of Chemical Weapons.
Neither body would comment on Wednesday, saying the situation "spoke for itself". The US Secretary of State John Kerry warned earlier this week that there would be "consequences" if the deal was not honoured.
Russia, which was instrumental in brokering the deal, played down the delays and said Syria would still move out a large quantity of chemicals by the end of this month.
The issue of the chemical weapons, one of the largest arsenals in the world, has been one of the most contentious themes of the civil war, which is now nearing a fourth year and showing no signs of slowing.
After face-to-face talks in Geneva last week failed to yield any substantive concessions, Russia said regime officials would attend a second round scheduled to resume on Monday. However, hopes of a diplomatic breakthrough appear dim as fighting continues in several parts of the country, particularly Aleppo.
Activists claim that more than 1,200 people have been killed there since the Geneva summit opened on January 22. Aleppo's high toll has been caused by clashes between rebel groups and a daily barrage of bombs, filled with shrapnel and fuel, dropped from helicopters.