US Secretary of State John Kerry said on Sunday that the United States would double its non-lethal aid to opposition forces in Syria to $250 million.
Kerry stopped short of a US pledge to supply weapons to insurgents fighting to overthrow Syrian President Bashar al-Assad. But he said that the rebels' foreign backers were committed to continuing support and had decided to channel all future aid through the insurgents' Supreme Military Council.
He added that "there would have to be further announcements about the kind of support that might be in the days ahead" if Syrian government forces failed to pursue a peaceful solution.
Speaking after a meeting of the Syrian opposition and its 11 main foreign supporters in Istanbul, Kerry said the United States would provide an additional $123 million in non-lethal assistance to the rebels, bringing the total of this kind of U.S. help to $250 million.
Kerry urged other foreign backers to make similar pledges of assistance with the goal of reaching $1 billion in total international support.
At a later news conference on Sunday afternoon, Kerry said he would push to ensure that new non-lethal military aid would be delivered as soon as possible.
Kerry said the equipment could include communications equipment, body armour, night vision goggles and medical supplies to assist the insurgents.
Other military supplies pledged by Kerry in late February, including ready-made meals and medical supplies, are only expected to be delivered by the end of this month.
Asked when the opposition could expect to receive the new supplies, Kerry told reporters:
"I can promise you that as soon as I return to Washington which is early this next week, I am going to press as hard I can to make sure that this is a matter of weeks that we are talking about...this has to happen as quickly as possible."
Kerry said he had discussed ways to break the logjams during meetings with the Turkish Foreign Minister Ahmet Davutoglu, who hosted the meetings on Saturday between the Syrian opposition and their foreign backers.
"I am quite confident that some of those logjams are going to be broken," he said.
Kerry also said that an agreement by the foreign backers to channel future military assistance via the opposition's Supreme Military Council headed by Brigadier Selim Idris, would speed the delivery of supplies.
"That's going to have a profound impact particularly in the south, where some items have been coming in but there hasn't been as good a level of coordination as perhaps there should have been," he said.
Speaking after the end of the "Friends of Syria" meeting overnight, Kerry said the crisis was in a "critical moment".
"The stakes in Syria couldn't be more clear: Chemical weapons, the slaughter of people by ballistic missiles and other weapons of huge destruction. The potential of a whole country, a beautiful country with great people, being torn apart and perhaps breaking up into enclaves (with the) potential of sectarian violence which this region knows there is too much of.
"What we are trying to do is to avoid all of that. And we committed to - we recommitted - because we think there are some people who don't believe that we believe it, or are in fact committed to it," he said.
Kerry referred to a statement issued after the meeting by Syria's main opposition National Coalition in which it pledged not to use chemical weapons, rejected "all forms of terrorism" and vowed that its weapons would not fall into the wrong hands.
In its declaration outlining its vision of a post-Assad Syria and issued following the meeting with Western and Arab backers, the coalition also said it would not allow acts of revenge against any group in Syria.
The latest US expansion of non-lethal aid follows Kerry's announcement in Rome in late February that Washington would shift policy to provide medical supplies and food directly to opposition fighters, an option it had previously rejected.
Despite pressure from some members of Congress and recommendations even from among his own advisers, US President Barack Obama has refused to supply arms to the rebels, reflecting concern that such weapons would fall into the hands of Islamist militants in the ranks of the fractious insurgency.