An Arab summit kicked off in Kuwait Tuesday with a call by Syria's opposition for "sophisticated" arms, while Saudi Arabia stressed the need for a change in military balance to "end the impasse".
UN peace envoy Lakhdar Brahimi, however, insisted on the need for a "political solution" to the conflict, urging an "end to the supply of arms to all parties".
The head of the Syrian National Coalition, Ahmed Jarba, repeated calls on the international community to supply rebels with "sophisticated weapons".
Saudi Crown Prince Sheikh Salman bin Abdulaziz, whose country is a major supporter of the Syrian rebellion against President Bashar al-Assad, accused the world of "betraying" the opposition by failing to arm them and leaving them as "easy prey".
Salman urged support for the rebels, insisting that a solution to the conflict, in which regime forces have recently made significant advances, required a "change in the balance on the ground to end the impasse".
The conflict in Syria, which in mid-March entered a fourth year, has killed more than 140,000 people and displaced millions.
Jarba told the summit that a decision not to hand over Syria's seat in the Arab League to the opposition sends a wrong message to Assad, telling him to continue "to kill".
The Syria government's brutal repression of protests which erupted in March 2011 resulted in its suspension from the Cairo-based Arab League.
Its seat was allocated to the National Coalition at the last summit, in Doha in 2013, but has not been handed over because, according to Arab League chief Nabil al-Arabi, the oppossition has yet to meet the legal requirements.
Qatar's Emir Sheikh Tamim bin Hamad al-Thani, in his address to the gathering, accused the Syrian government of lying in "pretending to accept a political solution" but was in fact "buying time".
Brahimi urged a revival of peace talks.
"I call upon Europe, the United Nations and the United States to take clear steps to reactivate the Geneva talks," whose last round broke off on February 15 without setting a date for further negotiations.
"There is no military solution," stressed Brahimi.
He had said on Monday that a further round of talks was "out of the question for the time being".
While the Syrian conflict is taking centre stage at the summit, a regional rift over Egypt's Muslim Brotherhood has been kept off the agenda.
The dispute pits Qatar against Egypt, Saudi Arabia, Bahrain and the United Arab Emirates and has apparently affected the level of representation at the two-day summit, which is being held in Kuwait for the first time.
Kuwait said 13 heads of state were attending the meeting, with low-profile representation from Kuwait's Gulf partners.
Efforts to settle the inter-Arab rift appear to have been placed on the back burner, with officials ruling out any compromise being struck in Kuwait.
Egyptian Foreign Minister Nabil Fahmi told reporters it was not possible to forge a compromise with Qatar during the summit because "the wound is too deep".
Kuwait's foreign ministry undersecretary Khaled al-Jarallah said the dispute between Qatar and its neighbours would "be resolved within the Gulf house", not at the summit.
Saudi Arabia, the UAE and Bahrain have recalled their ambassadors from fellow Gulf Cooperation Council member Qatar in protest at Doha's perceived support of the Muslim Brotherhood, branded a terrorist organisation by Cairo and Riyadh.
On the Palestinian issue, Arab leaders are expected to call for $100 million in monthly aid for the Palestinian Authority and to reject demands by Israel that Palestinians recognise Israel as a Jewish state.
Palestinian leader Mahmud Abbas, fresh from talks with US President Barack Obama in Washington last week, was to brief his Arab counterparts during the summit.