The regime of Syrian President Bashar al-Assad is being kept in power with ongoing help from Iran and its proxy militia in Lebanon, Hezbollah, the US secretary of state John Kerry warned on Saturday 22 June.
Kerry told a conference of the so-called "Friends of Syria" group in Doha, Qatar, that military support from Iran and Hezbollah was escalating the conflict.
"The continued bloodshed at the hands of the Assad regime and the increasing involvement of Iran and its proxy Hezbollah threaten the very prospects of a political settlement and of peace," said Kerry.
"The regime's use of chemical weapons crossed President Obama's and other nations' red lines. And we also condemn - all of us - any atrocity or any excess by any extremists or by any oppositionist group that might engage them."
Kerry said plans to arm the rebels were aimed at finding a political settlement, rather than a military one.
"Reliable civilian governments and a stronger and more effective armed opposition will better enable the opposition to be able to provide the counterweight to the initiative of Assad to reach out across borders, trans-boundary, to bring Iranians, to bring Hezbollah - again, a terrorist organisation - to the table."
As ministers from the US, UK, France Germany, Italy, Jordan, Saudi Arabia, Qatar, the United Arab Emirates, Turkey and Egypt attempted to thrash out details of what armaments to supply to the rebels, Britain's William Hague said the UK had not yet reached a decision.
"On the much debated question of whether we should give lethal aid of any kind to the Syrian opposition, the position remains the same. We have taken no decision to do that," said Hague.
"At the end, there is only a political solution for the conflict. We want to see a successful conference in Geneva," he said, referring to a joint US-Russian proposal for negotiations to be held in the Swiss city.
Hague said Britain's aim was to reach a political rather than military solution in Syria, after two years of civil war.
"The goal of the meeting is to be very concrete about the importance of every kind of assistance that's coming from the London 11 countries [the "Friends of Syria"]... being fully co-ordinated and going through only the Syrian opposition coalition," a US official told the Agence-France Presse.
French foreign minister Laurent Fabius said: "We will try in Doha to sum up the situation on the ground and to see how we can aid the opposition coalition and arrive at a political solution."
On the eve of the meeting, the armed opposition group the Free Syrian Army said they have taken delivery of new weapons that could "change the course of the battle" against the Syrian regime.
FSA spokesman Louay Muqdad told Al Arabiya TV that the first shipment of weapons had already been received.
"We have received the first shipment of weapons two days ago, following pledges by several countries, especially the United States," he said.
"The source of these weapons was some sister countries and other countries who made pledges," he added.
Muqdad said a plan to arm the Syrian rebels will be unveiled during the conference in Doha.
"It is a matter of days before we receive other weapons, as we were promised ... and the military support will continue to flow as long as the weapons are used in a disciplined way," he said.
"We've received quantities of new types of weapons, including some that we asked for and that we believe will change the course of the battle on the ground.
"We have begun distributing them on the front lines. They will be in the hands of professional officers and FSA fighters," he added.
Diplomatic sources said the conference would try to build on the momentum of the recent G8 summit to organise a conference known as Geneva 2.
The Friends of Syria meeting, which will not include the regime's most powerful ally, Russia, is expected to hear from an FSA general that rebel forces are losing ground to Assad's troops, despite modest diplomatic gains.