By Sami Aboudi and Yara Bayoumy
DOHA (Reuters) - To applause from Arab heads of state, a foe of Bashar al-Assad took Syria's vacant seat at an Arab summit on Tuesday, deepening the president's diplomatic isolation and diverting attention from rifts among his opponents.
Speaking at an annual gathering of Arab leaders in the Gulf state of Qatar, Moaz Alkhatib said he had asked U.S. Secretary of State John Kerry for American forces to help defend rebel-controlled northern parts of Syria with Patriot surface-to-air missiles now based in Turkey. NATO swiftly rebuffed the idea.
"It was a historic meeting," said Syrian opposition spokesman Yaser Tabbara. "It's a first step towards acquiring full legal legitimacy."
The 22-nation League lent its support to giving military aid to Syrian rebels. A summit communique offered some of its toughest language yet against Assad, affirming member states had a right to offer assistance "including military, to support the steadfastness of the Syrian people and the Free Army".
Alkhatib said the United States, which has given non-military aid to Syrian rebels, should play a bigger role in helping end the two-year-old conflict in Syria, blaming Assad's government for what he called its refusal to solve the crisis.
"I have asked Mr. Kerry to extend the umbrella of the Patriot missiles to cover the Syrian north and he promised to study the subject," he said, referring to NATO Patriot missile batteries sent to Turkey last year to protect Turkish airspace.
"We are still waiting for a decision from NATO to protect people's lives, not to fight but to protect lives," he added, addressing a body that barred Assad's government in late 2011.
Responding to Alkhatib's remarks, an official of the Western military alliance at its headquarters in Brussels said: "NATO has no intention to intervene militarily in Syria."
Turkey, which reported a mortar landing harmlessly on its border on Tuesday, said it was up to the rest of NATO to decide if members wanted to expand the remit of the Patriot batteries.
Michael Stephens, a researcher based in Qatar for Britain's Royal United Services Institute, said acceding to Alkhatib's request would effectively put NATO at war with Damascus.
NATO's current deployment of three Patriot missile batteries in southern Turkey is intended to be purely defensive. The Patriots are designed to shoot down hostile missiles in mid-air.
Alkhatib, a Sunni Muslim cleric, took Syria's seat at the summit for the first time despite announcing on Sunday that he would step down as leader of the Syrian National Coalition.
Behind him sat Ghassan Hitto, the prime minister of a provisional opposition government that plans to run rebel-held area, and fellow senior opposition official George Sabra.
Alkhatib made a blunt call on other Arab leaders to "fear God in dealing with your people" and free political prisoners - a departure from anodyne tradition at the League.
But he also criticized what he called Western failure to bring an end to the conflict, and said an influx of foreign Islamist fighters should not be used by the West as a pretext to deny Syrians meaningful help. He denounced the presence in Syria of Iranians and Russians he said were backing the government.
Speaking at a news conference at the end of the summit: Qatar Foreign Minister Sheikh Hamad bin Jassim al-Thani defended the summit's support for arming the rebels, saying that while it was not a "preferable" policy there appeared little alternative.
"We have done all we could to find a peaceful solution," he said. "Unfortunately this solution did not come because ... the regime was betting on a solution by force."
But Kofi Annan, the former U.N. chief who tried to mediate an end to the fighting, said he expected little outside military intervention. He told an audience in Geneva: "We left it too late." He added: "The Syrian people ... are waiting for the killing to stop ... As late as it is, we have to find a way of pouring water on the fire, rather than the other way around."
He described as a "gross underestimate" the United Nations figure of 70,000 killed in a conflict that began with anti-Assad protests and turned into a sectarian-tinged armed insurrection.
The war in Syria has divided world powers, paralyzing action at the U.N. Security Council. The Arab world is also split, with Saudi Arabia and Qatar the most fervent foes of Assad, and Iraq, Algeria and Lebanon the most resistant to calls for his removal.
The conflict echoes strains between Sunni Muslims, notably in the Gulf, and Shi'ites, in Iraq, Lebanon and non-Arab Iran, whose faith is related to that of Assad's Alawite minority.
Syrian rebels again fired mortar rounds into central Damascus on Tuesday. State television said several people had been wounded by "terrorist" mortar bombs that landed in the Syrian Arab News Agency SANA compound in the Baramkeh district.
State television said a suicide car bomber killed and wounded several people in northeastern Damascus, although opposition activists said the blast could have been a mortar.
Syrian state TV did not cover the Arab League meeting in Qatar, airing a program on makeup for women instead.
A group of pro-Assad hackers signing themselves the Syrian Electronic Army claimed an attack on an Arab League website that directed readers to a picture of Assad and derided the League's Egyptian secretary-general for his "loyalty to the sheikhs".
Alkhatib's decision to quit, which he blamed on the world's failure to back the armed revolt against Assad also appeared to be motivated by internal disputes in the alliance. It undermined the alliance's claim to provide a coherent alternative to Assad.
Liberals saw it as a protest against what they view as the rising influence of hardline Islamists in the Qatari-backed umbrella group set up in Doha in November.
Jane Kinninmont, of Britain's Chatham House think-tank, said Qatar and the other Gulf states had been frustrated that the United States in particular and also European powers had not done more to help the Syrian opposition.
"The Gulf countries contrast this to the Iraq war which many of them were quite dubious about," she said. "And they see a U.S. that's far less interventionist today, even though there's a much greater case for and immediate humanitarian need."
(Additional reporting by Mirna Sleiman and William Maclean, Omar Fahmy in Cairo, Oliver Holmes and Erika Solomon in Beirut, Gulsen Solaker in Ankara, Stephanie Nebehay in Geneva and Adrian Croft in Brussels; Writing by Alistair Lyon; Editing by Alastair Macdonald and Jon Hemming)