Russia has been accused by Western diplomats of reneging on a pledge to stop supplying arms to the Syrian regime. The assurances made over a month ago were presented by British officials as a sign that the Kremlin was distancing itself from President Bashar al-Assad and his ruling coterie.

The flow of arms has, however, continued unhindered with the Russians stressing that there was no United Nations prohibition on supplies and it was simply fulfilling its contractual obligations. As well as air- and naval-defence systems, the Kremlin may now be preparing to send Yak-130 jets which can be fitted with missiles to carry out ground attacks, according to American and European officials.

The Syrian regime has extensively used warplanes to carry out raids on heavily populated areas, leading to dozens of civilian casualties. Russia's state arms agency holds a $550m contract to supply 36 of the Yaks, which are trainers but can also be used on combat missions. Last year, a Russian-operated ship carrying helicopter gunships and air-defence missiles was forced to turn back to Russia, after its British insurers withdrew coverage. The aircraft were subsequently sent through a different shipping company.

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While the Assad regime continues to receive weapons, from Iran as well as Russia, a British attempt to provide military aid to the Syrian rebels failed at a European Union meeting in Brussels today.

There was agreement, instead, on an amendment which would allow more "non-lethal" assistance to the opposition. But the outcome of the meeting in Brussels made it very clear that David Cameron's Government had been isolated in its efforts to strengthen militarily the moderate revolutionary factions, who have been increasingly sidelined by jihadist groups receiving arms and money from backers in the Gulf states.

Russia has insisted that it is within its rights to keep arming the regime as there are no UN resolutions prohibiting this. Anatoly Isaikin, the director of Rosoboronexport, said: "In the absence of [UN] sanctions, we are continuing to fulfil our contract obligations. We are mostly shipping air-defence systems and repair equipment intended for various branches of the military."

However, it is the Syrian regime's air defences, overhauled and upgraded with Russian help, which have been a powerful deterrent against the West declaring a "no-fly zone" of the type which, after it became a bombing campaign, brought down Muammar Gaddafi in Libya.

Western officials also claim that Moscow has refused to provide full details of the contractual obligations they have to fulfil and there is also evidence that the regime is getting further Russian arms through third parties.

Critics point to the British proposal on arming the rebels as an example of lack of clarity in the Western approach. The move had been opposed from the outset by Germany and Scandinavian countries as well as by Baroness Ashton, the British head of EU foreign affairs. "There is no shortage of arms in Syria," said Jean Asselborn, the Luxembourger Foreign Minister.

The French, who had backed the UK position, have become more lukewarm since the troops they sent to Mali found Western arms supplied to Libyan rebels in the jihadist arsenal. Yesterday, the Hollande government seemed satisfied with the agreement on non-lethal aid. "Technical assistance and protection of civilians will be easier," said Foreign Minister Laurent Fabius.

In the US, the outgoing Secretary of State, Hillary Clinton, had advocated arming the rebels. The new defence secretary, Leon Panetta, also backed the move and stated that the head of US military, General Martin Dempsey, was also on board. However, General Dempsey and Barack Obama have publicly urged caution in the past over getting entangled in Syria.

The Russians, on the other hand, insist that their opposition to UN resolutions against the Assad regime, bitterly criticised by the US and Britain, has not stopped the building of growing links with the Syrian opposition.

Ahmad al-Khatib, the head of the Syrian National Coalition for Opposition Forces – set up at the instigation of the West to replace the Syrian National Council, which had become faction-ridden – has offered to hold direct talks with the regime.

Today, Ali Haidar, Mr Assad's minister for national reconciliation, responded: "We, the government and me personally, will meet, without exceptions, Syrian opposition groups inside and outside Syria."

It remains to be seen whether the talks will actually take place, but UN Under-Secretary-General for Political Affairs Jeffrey Feltman held the offers were "the most promising thing we've heard on Syria recently".