The Assad regime suffered the most significant defection of the Syrian uprising on Thursday when a general from one of the country´s most famous families decamped to join the rebels.

The desertion of Brig Manaf Tlas, a senior commander in the elite Republican Guard, dealt a humiliating personal blow to President Bashar al-Assad and represented a major scalp for the opposition.

Brig Tlas was once a close confidante of the president, serving as a member of Mr Assad´s small inner circle and the central committee of the Syria´s Ba´ath Party.

A pro-government website with links to the Syrian security services confirmed the defection, saying that Brig Tlas had fled to Turkey but played down the impact of the development.

"His escape does not mean anything," a security official was quoted by the Syriasteps website as saying.

But the brigadier´s defection would have reverberated across Syria because of the pedigree of his family name. Opposition sources claim 15 brigadiers have joined rebels camped near the border in recent months.

But Brig Tlas is by far the most significant of these defectors. Gen Mustafa Tlas, his father, was a long-serving defence minister and one of the most powerful people in Syria, playing a pivotal role in consolidating the president´s hold on power after he succeeded his father, Hafez al-Assad in 2000.

The defection could prompt other members of the Sunni elite who have remained loyal to the president to follow suit.

In an indication the move had been feared, Brig Tlas had been sidelined last year. He remained at home in Damascus for months amid rumours that he was under arrest after questions over his loyalty were raised in part because of the actions of other members of his family.

One of his cousins serves as the commander of a rebel brigade in Homs, while his brother and father, said to nurse a grudge against Mr Assad after he was forced to resign in 2004, now live in Paris and are said to associate with regime opponents.

The defection came as Iraq´s foreign minister disclosed that Al Qaeda militants at the forefront of Iraq´s former insurgency had crossed the border into Syria and are fuelling the violence there.

Hosyhar Zebari said he had "solid information" that extremists affiliated to the terror network had re-opened cross-border smuggling routes that sustained Islamist militancy during Iraq´s bloodiest years. "Most of the suicide bombers, foreign fighters, elements of al Qaeda used to slip into Iraq from Syria," he said.

"Now it´s the opposite. Now their direction is the other way round." Mr Zebari, one of the Arab world´s most respected diplomats, gave warning that the militant migration posed a grave danger to the region because the extremists could use Syria as a base to launch attacks elsewhere in the Middle East.

His minister´s assessment is likely to challenged by rebel leaders in Syria, who accuse the Assad regime of deliberately overstating the level of al-Qaeda loyalists operating in the country.

Iraq´s Shia-led government is seen in the Arab world as an ally of President Bashar al-Assad. Although its support of his regime is more quietly stated than Iran´s, Iraq has refused to back Arab League initiatives against the Syrian government.

Mr Zebari´s assessment is shared by Western diplomats who have spoken of concerns over the growing presence of Iraqi-based extremists in Syria.

Groups pledging allegiance to al-Qaeda have claimed responsibility for bombings against civilian targets in Damascus and Aleppo, Syria´s second city, that have killed scores of people.

The presence of al-Qaeda extremists has discouraged Western powers from giving greater assistance to the rebels in the past amid fears that weapons could end up in Islamist hands.

CIA officers working in southern Turkey have reportedly been working to ensure that arms provided by Saudi Arabia, Qatar and the United Arab Emirates are channeled to rebel groups seen as more moderate in their outlook.

However Amnesty International yesterday urged caution about the distribution of weapons to the rebels as it called for a complete arms embargo on the Assad regime on the eve of today´s meeting of the "Friends of Syria" coalition.

Switzerland announced that it would block arms shipments to the United Arab Emirates after the publication of photographs of a Swiss- made hand grenade that was found in Syria -- suggesting that the UAE had broken a promise not to re-export Swiss arms.

Western powers are hoping that the Friends of Syria meeting will result in fresh pressure on Mr Assad after a new international initiative failed explicitly to call for his resignation following objections from Russia.

William Hague, the Foreign Secretary, said that the Friends of Syria meeting would be used to lay the ground for a new United Nations Security Council resolution that would threaten the Assad regime with tough sanctions.

Mr Hague told members of the public in a live conversation on Twitter that the Government would seek a new resolution even without the backing of Russia and China, both of whom wield veto power in the Security Council.

The West has attempted to shame Russia and China by forcing them to vote against Security Council measures twice in the past, but the strategy appears to have made little difference in ending the impasse over Syria.

Sergei Lavrov, the Russian foreign minister, on Thursday confirmed that the West had approached the Kremlin to ask it to give Mr Assad asylum. Mr Lavrov said he assumed that the proposition was a "joke". (© Copyright of Telegraph Media Group Limited 2012. 07/06/12)