Saudi Arabia and Qatar share the West's alarm at the rise of al Qaeda-aligned groups in Syria, but say the answer is for outsiders like them to be more involved in backing rebels there.
The two Gulf Arab states rooting for President Bashar al-Assad's overthrow appear to be chafing at Western pressure to keep out of the fight, arguing that building ties through aid and advice to favoured opposition groups is the only way to ensure other, hardline Islamist factions are sidelined.
The United States and Europe want to avoid arming rebel militias for fear that weaponry will find its way to ultra-orthodox Sunni Muslim groups close to jihadis like al Qaeda.
Assad cites such militants, often seen as the most effective fighters on Syria's battlefields, to justify using relentless force in a two-year old war that has cost some 70,000 lives.
Attacks carried out by such groups against the Alawite minority, an offshoot of Shi'ite Islam that dominates Syria's power and security structures, have aggravated sectarian rifts in many Arab states including some in the oil-rich Gulf.
The United States in December listed the al Qaeda-endorsed al-Nusra Front in Syria as a terrorist group.
But Saudi Arabia and Qatar are signalling that the longer the war drags on, the stronger such hardliners will get, while other groups will likely struggle if denied meaningful aid, according to a Gulf Arab official, analysts and diplomats.
Gulf Arab policymakers argue that hastening Assad's fall will curb the militants' influence, and, a related bonus, reduce the regional clout of the Syrian leader's ally Iran.
Saudi Foreign Minister Saud al-Faisal bluntly told a news conference in Riyadh on February 12: "My country believes that the brutality of the Syrian regime against its own people requires empowering the people to defend itself."
On Tuesday Qatari Prime Minister Sheikh Hamad bin Jassim bin Jabr al-Thani said: "As there is no clear international opinion to end the crisis in Syria... we are supporting the opposition with whatever it needs, even if it takes up arms for self-defence."
A Gulf Arab official, who asked not to be named, said it was vital to build ties to non-Qaeda rebel groups to strengthen them now and in any future fight for power in a post-Assad Syria.
Mustafa Alani, a Gulf-based security analyst, said arms were now more available in Syria and what such groups needed most was non-lethal aid such as food and medical aid for their families.
"The Gulf is waiting for a green light - they want the West to lift this veto on supplies," he said.
Gulf Arabs are not bound by US and EU arms embargoes on Syria, and some analysts say they supplied weapons to Syria last year, probably through tribal and smuggling connections in Iraq.
But Saudi Arabia and Qatar have signalled any support would be much more effective if Western powers lent political backing, coordination, equipment and advice.
Western nations, mindful of how weapons spread from Libya after its Western-backed revolt in 2011 to unstable nations such as Mali, say arming rebels is risky because it is hard to tell militants from moderates in a disorganised array.
Gulf Arabs say they know Islamist armed groups better and blame disorganisation on a lack of outside support and training.
Riyadh-based political scientist Asaad Shamlan said rising militancy among Syria's opposition was a result of not engaging with rebels more openly, and suggested Gulf Arabs must act.
"What is the strategic objective? It's to enable the opposition to overthrow the Assad regime? Then a certain amount of risk has to be taken," he said.
In January a former Saudi intelligence chief, Prince Turki al-Faisal, publicly called for Syrian rebels to be given anti-tank and anti-aircraft weapons to "level the playing field".
Last month he said it would be possible to "make the weapons reach the right people". Sophisticated weapons that relied on electronics could be deactivated remotely using wireless signals if they ended up in untrustworthy hands, he said.
Not all Gulf Arab states are eager to arm Syrian rebels, but all fear possible "blowback" if their own nationals go to fight in Syria and one day come home and launch a jihad for a purist Islamic state. The al-Nusra Front has ideological overlaps with al Qaeda, which has sworn to topple the Saudi ruling family.
In the 1980s Saudi rulers supported US-backed Islamists fighting Soviet forces in Afghanistan, a factor in the creation of al Qaeda, and in the last decade they turned a blind eye to clerics who urged Saudis to join an anti-US jihad in Iraq.
In 2003 Saudis who had fought in both conflicts launched attacks at home, drawing a tough security response from Riyadh.
Saudi Arabia's Grand Mufti, Sheikh Abdul-Aziz bin Abdullah Al al-Sheikh, cautioned Saudi youth against going to Syria for jihad, and advised prayer, and sending material support by "regular channels", al-Jazirah daily reported on January 7.