The backing occurred at a conference in Morocco.
Syrian opposition, fighting to topple President Bashar al-Assad, secured a major breakthrough, Wednesday, winning the recognition of more than 100 countries.
The development heralds the possibility for greater assistance for the fighters. The two-year war, which began as protest for more government concessions, has killed over 40,000 people, rights groups say.
The backing for the opposition came at an international conference of the “Friends of the Syrian People” in Morocco on Wednesday.
Major world powers including the United States and the United Kingdom gave the recognition, joining France which had earlier recognized the opposition group as the legitimate representatives of the Syrian people.
French Foreign Minister, Laurent Fabius, said the meeting in Marrakesh had made “extraordinary progress”, Television channel, Al Jazeera, reported.
Mr. Fabius said the European Union will be renewing its weapons embargo on Syria every three months, rather than annually, to be more flexible as the situation on the ground changes.
“The fact that the coalition, which is asking for the right to defend itself, is now being recognized by a hundred countries – yesterday the US and first France – I think this is a very important point,” he was quoted by the TV channel as saying.
But the opposition issued a cautious response to the development saying they were looking for more tangible backing to help oust Mr. Assad and also calling for the prosecution of members of the government.
The conference also repeated the warning on the use of chemical weapons saying it “would draw a serious response” from the international community.