NEW YORK (AFP) - The world powers most implicated in Syria's bloody civil war met on Friday to renew efforts to bind Bashar al-Assad's regime and its rebel foes into a peace deal.

Convened by US Secretary of State John Kerry, Russia's Foreign Minister Sergei Lavrov and UN Syria envoy Staffan de Mistura, 17 foreign ministers gathered at a New York hotel.

It was the first meeting of the International Syrian Support Group since Saudi Arabia brought together a coalition of Syria rebel and opposition groups to form a negotiating team.

If the group gives its support to Saudi Arabia's plan to form a rebel delegation, pressure will mount on Russia to bring its ally Assad to the table for talks on a political transition.

"Here in New York we will be seeking to harmonise as much as possible the opposition position with what we discussed in Vienna," German foreign minister Frank Walter-Steinmeier said.

Under the Vienna process agreed last month, there would be a six month political transition period once a ceasefire began - but the rebels demand that Assad step down immediately.

Russia has dismissed this idea and Kerry admitted this week in Moscow that it was a "non-starter."

"The most important task is to move forward towards a real ceasefire," Steinmeier added, in a broadcast by his ministry.

Aside from the hosts, the ISSG meeting brought together Britain, the UAE, Turkey, Saudi Arabia, Qatar, Oman, Lebanon, Jordan, China, Egypt, Germany, France, Iran, Iraq and Italy.

The European Union, the Organisation of the Islamic Conference and the Arab League were also represented.

Later in the day, the envoys were to head across town to the United Nations to seek UN Security Council approval for the Vienna peace plan.

A diplomat from one of the Council's permanent five members told reporters that wording of the resolution was not complete but that he expected it would pass.