UN Secretary General Ban Ki Moon said on Thursday time was running out for Syrian President Bashar al-Assad to act on a UN-backed peace plan for the country, where government forces continued a crackdown on rebels.
"It is essential that President Assad put those commitments into immediate effect. The world is waiting for commitments to be translated into action. The key here is implementation, there is no time to waste," Ban told an Arab League summit in Iraq.
Ban said Assad must act to divert his country from a "dangerous trajectory" which put the entire region at risk.
Syria accepted the peace plan proposed by UN and Arab League envoy Kofi Annan but violence has continued.
Syrian opposition groups say at least 40 people have been killed since government troops seized the northwestern town of Saraqeb over the weekend.
More than 9,000 people have died in Syria since pro-democracy protests erupted a year ago.
The Damascus government insists it is combating "armed terrorist gangs" who are seeking to destabilize Syria.
Nine Arab heads of state are attending the summit in Baghdad, the first to be held there in decades.
An explosion was heard in central Baghdad as the talks were starting, al Jazeera television reported.
"It was a mortar round that landed near the [Iranian] embassy. There are no casualties," a police official said.
In another development, Russian President Dmitry Medvedev said the BRICS nations - Brazil, Russia, India, China and South Africa - would not allow outside intrvention in Syria, and that solution in the country could only be achieved through dialogue.
