Syrian opposition officials say that 34 Hezbollah fighters were killed in battles near the Damascus area on Saturday. In total, over 100 people died in the war-torn country over the weekend.
It is estimated that over 100,000 Syrian combatants and civilians have died since the uprising against the regime of Bashar Assad began two years ago.
Washington wants Western and Arab allies to commit to directing all aid to Syrian rebels through the Western-backed Supreme Military Council, a senior US official said before talks in Qatar on Saturday, to try to reduce the power of jihadi groups.
Speaking before US Secretary of State John Kerry arrived in Doha for the meeting with European and Arab foreign ministers, the official said the United States was also seeking to ensure that aid promises for the tens of thousands of refugees fleeing the conflict are honored.
US President Barack Obama announced last week that Washington would step up military aid to rebels following a series of counter-attacks by Assad's forces, including the recapture of a strategic border town in an offensive led by Lebanese Hezbollah guerrillas.
Rebels say they urgently need advanced arms, including anti-tank and anti-aircraft weapons, to stem Assad's advance.
Western countries hope by channeling assistance through the council - the rebel military leadership headed by General Salim Idriss, a former commander in Assad's army - they can reduce the influence in the opposition ranks of radical Islamist groups such as the al Qaeda-linked Nusra Front.
The meeting in Qatar brings together ministers of 11 countries that make up a pro-rebel alliance - France, Germany, Egypt, Italy, Jordan, Qatar, Saudi Arabia, Turkey, United Arab Emirates, Britain and the United States.
"The goal of the meeting is to be very concrete about the importance of all assistance, every kind of assistance that is coming from 11 countries," the senior US official told reporters travelling with Kerry.
"It is important that it be fully coordinated and go through only the Syrian opposition coalition, specifically the Supreme Military Council," the official said.