Delegates from more than 60 countries gathered in Tokyo on Friday, seeking to ramp up pressure on Bashar al-Assad's regime as the US moved towards recognising the newly-unified opposition as true leaders of Syria.
Japanese foreign minister Koichiro Gemba, told the 'Friends of Syria' group the international community had to act together where the divided United Nations Security Council had failed.
"The violence has continued for more than 20 months and the number of casualties in Syria has surpassed 40,000 and counting today, causing a humanitarian crisis," he told representatives from 67 countries.
"We are gravely concerned about the spillover of the crisis to the entire region.
"While the United Nations Security Council has been unable to assume its primary responsibility, it's increasingly important for the international community to act as one in order to deal with" the continuing violence.
The Friends of Syria group has previously organised four such meetings -- in Paris in April, Washington in June, Doha in July and The Hague in September.
The fifth 'sanctions working group' meeting in Tokyo saw the first participation from four countries -- Kazakhstan, Kosovo, Indonesia and Bangladesh, a foreign ministry official said.
On Thursday US secretary of state Hillary Clinton said Washington was weighing what further help it could give the Syrian opposition rebels.
"We are going to carefully consider what more we can do," Clinton told a Washington forum, saying the United States was constantly evaluating the situation and adding: "I'm sure we will do more in the weeks ahead."
But she stopped short of saying whether the United States would recognise the newly-formed Syrian National Coalition, which is seeking to oust Assad, as the sole representative of the Syrian people, as several European countries have done.
Privately, US officials have said the Obama administration will likely go ahead and recognise the group at some point.