West considers action on Syria as America says it will arm rebels after nerve-gas attacks

Western nations took a big step on Friday towards supplying arms to Syrian opposition groups after the United States warned Bashar al-Assad’s regime it had crossed a “red line” by mounting deadly nerve-gas attacks against rebel fighters.

On Friday evening, David Cameron discussed the situation in Syria in an hour-long video conference with Mr Obama, the German Chancellor Angela Merkel, the French President François Hollande and the Italian Prime Minister Enrico Letta ahead of the G8 summit.

Earlier, Britain and the US spelt out details of chemical weapons atrocities blamed on Syrian government troops and signalled the time had come to bolster support for moderate groups resisting Assad’s forces.

The deepening sense of crisis over the two-year civil war will eclipse the G8 summit of world leaders taking place next week in Northern Ireland.

It has been heightened by the Syrian army’s recent successes in reversing the gains of rebel fighters and signs that Assad’s soldiers are preparing a major offensive against the opposition-held city of Aleppo.

There were signs of a concerted US-European effort to persuade the Russian President, Vladimir Putin, to abandon his support for the Assad regime. One UK source said: “Pressure is building – and not just on Assad.”

The Kremlin dismissed US claims of evidence that the Assad regime had used nerve gas, resulting in the death of up to 150 people. “I will say frankly that what was presented to us by the Americans does not look convincing,” said Mr Putin’s senior foreign policy adviser, Yuri Ushakov.

Mr Putin will hold talks in Downing Street on Saturday ahead of the G8 meeting beginning on Monday. The carnage in Syria, which has already cost up to 100,000 lives, looks certain to eclipse the summit’s formal agenda.

The announcement by the White House that it has clear evidence the Assad regime had used chemical weapons raised diplomatic tensions.

The US government received strong backing from Mr Cameron, who disclosed that Britain had confirmed the “abhorrent” nerve agent sarin had been used against rebel fighters on two occasions – at Utaybah on 19 March and at Sheikh Maqsood on 13 April.

The US ambassador the UN, Susan Rice, also delivered a letter to the UN Secretary-General, Ban Ki-moon, detailing the use of chemical weapons. The letter stated that sarin gas was used by government forces twice in March in and close to the city of Aleppo, a rebel stronghold.

Britain, the US and France are all moving towards supplying moderate elements of the Syrian opposition with weapons, which initially could include anti-tank missiles, small arms and ammunition. Other options include the establishment of some limited kind of no-fly zone over portions of the country, air strikes on government airfields and strikes by cruise missiles.

Washington declined to offer more specifics on Mr Obama’s decision to send lethal aid to moderate rebels. No final decisions have been made on the type of weaponry to be sent, or when it would reach the rebels.

The seriousness of the situation was underlined last night with reports that 300 US Marines have been sent to northern Jordan in a move that paves the way to arming rebel groups. A Patriot anti-aircraft missle system has also, according to The Times, been deployed to the area.

The Deputy National Security Adviser Ben Rhodes, who announced Mr Obama’s decision late on Thursday, said last night that the ultimate goal of the US is that Assad should “leave power”, and stressed that the US hoped to see this achieved through a process of political negotiation. He added: “The leader of Syria has no legitimacy among his people.” The shorter-term purposes of the decision to arm the rebels, he said, in addition to strengthening moderate opposition forces, was to “send a signal to the Assad regime that there are consequences” to using chemical weapons.

The Syrian government dismissed the US charges that it used chemical weapons as “full of lies”, and accused President Obama of resorting to “fabricated information” to justify his decision to arm the rebels. The statement, issued by the Syrian foreign ministry, also accused the US of having “double standards”, saying America claims to fight terrorism while supporting Jabhat al-Nusra (also known as the Nusra Front), an al-Qa’ida affiliate which has emerged as one of the most effective fighting factions on the rebel side in Syria.

Meanwhile, the commander of the main Western-backed rebel group welcomed the US move.

“We hope to have the weapons and ammunition that we need in the near future,” General Salim Idris told Al-Arabiya TV, adding that the move boosts “the rebels’ morale”.

The leader of Lebanon’s Hezbollah group vowed to keep fighting in Syria “wherever needed”. Iran-backed Hezbollah fighters have played a key role in recent regime gains in Syria, including the recapture of the important strategic city of Qusayr.

“We will be where we should be, we will continue to bear the responsibility we took upon ourselves,” Sheik Hassan Nasrallah said in a speech to supporters in southern Beirut.

US Senator John McCain, who has advocated more direct intervention in the conflict, decried the fact that the US had taken so long to take any action at all. “It’s disgraceful, the conduct of the United States sitting by and watching this happen,” he said. He said the response was inadequate.

Some American military analysts said the aid which may be offered at this point could make little difference to the direction of the conflict. “Small arms and ammunition will certainly not change the military balance on the ground inside Syria,” noted Mona Yacoubian, a former US State Department official and now Syria analyst at the Stimson Centre in Washington. “The provision of sophisticated, heavy weapons could begin to change that, although that option is fraught with risks.”

Moves to support moderate rebels are believed to have the backing of two other G8 members, Italy and Canada. Germany would not supply weapons, but is understood not to oppose the move by other nations.

Mr Ban warned that there could be no military solution to the conflict and increasing the flow of arms to either side “would not be helpful”. He said: “The validity of any information on the alleged use of chemical weapons cannot be ensured without convincing evidence of the chain of custody.”

Mr Cameron repeated that the UK had taken no decision to arm moderate rebels following the lifting of the EU weapons embargo on Syria, but said the Government would “continue to support, train and assist and work with the opposition”.

The Prime Minister will face an uphill struggle to win political support in Britain for arming rebel forces. Disquiet over the potential move cuts across all major parties and, as disclosed by The Independent last week, includes Conservative Cabinet ministers. Ms Merkel said the UN Security Council should be summoned to reach a joint position on Syria.