Paris - Britain, France and the United States on Monday agreed to step up their backing for rebels fighting Syrian President Bashar Assad.
The three powers also agreed at talks in Paris that Assad would face "serious consequences" if he fails to comply with a UN resolution setting out a timetable for the handover of Syria's chemical weapons to international control, French Foreign Minister Laurent Fabius said.
In a slight difference of emphasis, US Secretary of State John Kerry did not use the word "serious", saying: "If Assad fails to comply with the framework, we are all agreed that there will be consequences."
Fabius announced there would be a major international meeting with leaders of the Syrian National Coalition in New York next week.
"We know that in order to negotiate a political solution, there has to be a strong opposition," Fabius said.
Kerry also stressed that the allies were "committed to the opposition" and said Assad had "lost all legitimacy to be possible to govern his country".
The signal of support for the rebels came in reaction to criticism of the chemical weapons deal from opposition leaders who fear it could consolidate Assad's grip on power.