With no sign of the west relaxing its ban on arming opposition forces, rebels are forced to focus on a gradual war of attrition

Despite widespread pledges of support from western and Arab states, the main Syrian opposition coalition says it has still not seen any significant increase in funding or arms supplies.

Members of the National Coalition for Syrian Revolutionary and Opposition Forces, formed in November, say that there is still no sign of western capitals relaxing their ban on delivering weapons to the rebels and even Gulf Arab governments, which helped arm opposition groups last year, are supplying less each week.

"The supplies are drying up. It is still Syrian expats – individuals – who are providing the funding by and large," said a Syrian businessman who has helped fund the opposition since the uprising began 22 months ago.

As a result, he said, the fragmented rebel forces have given up hopes of a sweep through the country and are focusing instead on a gradual war of attrition: besieging isolated government military bases to stop the regime using planes and helicopters against them and ultimately to capture weapons, to compensate for the meagre supplies from abroad.

Opposition groups claim to be close to overrunning a regime helicopter base near the northern town of Taftanaz, in Idlib province, posting a video online purporting to show a captured tank firing at government armoured vehicles and helicopters inside the perimeter walls of the base.

"The battles now are at the gates of the airport," Fadi al-Yassin, an activist based in Idlib told the Associated Press, adding that the base commander, a brigadier general, had been killed in the fighting on Thursday.

Yassin said that it had become very difficult for the regime helicopters to take off and land at the base, but warplanes from airfields further south, in the central province of Hama and the coastal region of Latakia, were bombarding rebel fighters besieging Taftanaz.

President Bashar al-Assad's government also claimed to be advancing in Daraya, a Damascus suburb close to another military air base and some government headquarters.

As it has become increasingly clear that large-scale external assistance is unlikely to materialise, the many locally-based rebel groups have found ways of sustaining themselves militarily and financially, but have largely given up hoping for a sudden breakthrough.

"What you are going to see is one or two air bases beginning to fall, particularly in the north, in Aleppo and Idlib," the opposition financier said. "But there is a law of diminishing returns. As these bases are encircled there is less bounty in each one as the government has been moving out assets when it becomes clear the bases are going to fall."

In November, the rebels succeeded in bringing down some government aircraft with shoulder-launched missiles captured in a regime base, but Peter Bouckaert of Human Rights Watch said sightings of such missiles had faded in recent weeks. "There was a spike late last year, but there have been no signs of any more since that capture, and there is no evidence we have seen of foreign-supplied missiles," he said.

Over the past two months, the US, UK and France as well as other European states and the Gulf monarchies have declared the newly formed national coalition "the sole legitimate representative of the Syrian people", in what they hoped would be a turning point in bringing some cohesion to the deeply divided opposition and in forging links between those in exile and rebel commanders inside Syria.

Such links have continued to be elusive, however, and the new coalition and its backers are blaming each other, in rows reminiscent of the problems that dogged its forerunner, the Syrian National Council.

Western governments have made disbursements of aid dependent on proven control over rebel forces in Syria and credible assurances that the assistance would not further the aims of extremist Islamist groups such as the Nusra Front, declared a terrorist organisation by the US. Opposition leaders complain that without significant aid they have little hope of rallying support or exerting any control over the chaotic anti-Assad effort.

"We don't even money for airplane tickets," one complained.

"It is little unfair of the international community and particular the French to bestow this title [of sole legitimate representative] on the coalition and not follow through," said Salman Shaikh, of the Brookings Institution's Doha centre thinktank, which played a role in bringing together disparate Syrian activist and opposition groups last year. "If they cannot provide for people in the north, which I suspect will come under full opposition control this year, then the people on the ground will question what is the point. And what you will get is just more factionalism."

He added: "I see a very dark period ahead of us, with a total breakdown like Iraq in 2006, with sectarianism on a scale we have not yet seen in Syria."

Mustafa Alani, the director of the national security and terrorism studies department at the Gulf Research Centre, said: "The people fighting on the streets are not controlled by people outside. They feel they can topple the regime without any help. They feel they are able to self-finance and self-arm and they can survive.

"Their focus has shifted. Their strategy is not to try to hold villages and towns so much, but to concentrate on air bases, to stop the aircraft flying and to build up pressure in Damascus. That is where the war will be decided."