A veteran US senator has urged Washington to launch airstrikes against Syria's military in response to its use of heavy artillery to bombard and devastate residential areas in protest hubs across the country.
Speaking in the Senate on Monday, John McCain said US President Barack Obama had been too soft on Damascus and cited moral and strategic obligations to help force the government of Bashar al-Assad, the Syrian president, out of power.
The Republican, who stood against Obama for the presidency in 2008, said that helping arm the Free Syrian Army and other opposition groups would not be enough to "stop the slaughter of innocent civilians" and pave the way for democratic transition.
In-depth coverage of escalating violence across Syria
"Providing military assistance to the Free Syrian Army and other opposition groups is necessary. But at this late hour, that alone cannot be sufficient to stop the slaughter and save innocent lives," he said.
"The only realistic way to do so is with foreign air power."
McCain said the US should use its "full weight of air power" to crush Syria's year-long crackdown on dissent that has claimed thousands of civilian lives.
"The United States should lead an international effort to protect key population centres in Syria, especially in the north, through airstrikes on Assad's forces," he added.
"The benefit for the United States of helping to lead this effort directly, is that it would allow us to better empower those Syrian groups that share our interests. Those groups that reject al-Qaeda and the Iranian regime, and commit to the goal of an inclusive, democratic transition, as called for by the Syrian National Council."
McCain has long been more hawkish than both the Obama administration and his fellow legislators in his advocacy of the use of US military power to back uprisings against repressive governments.
Last year, he called for the US and NATO to step up its air campaign in Libya and support for rebels fighting against Muammar Gaddafi, describing forces battling to topple the country's longtime leader as "heroes".
Refugees flee to Lebanon
McCain's appeal came after the UN refugee agency said that about 2,000 Syrian refugees had crossed into neighbouring Lebanon over the last two days to flee the government's crackdown on opposition strongholds.
In the hillside town of Arsal in Lebanon's Bekaa Valley, residents said between 100 and 150 families had arrived from Syria on Sunday in one of the biggest refugee influxes so far from Syria into the country.
A dozen families spent Sunday night in a three-storey apartment block in Arsal after fleeing what they said was a
sustained army attack on the Syrian town of Qusair with tanks, rocket-propelled grenades and helicopters.
"Yesterday, they strengthened their siege on us and started bombing us from the air (with helicopters) and started pursuing the families with the helicopters and they struck...there were a lot of wounded and casualties," one refugee said.
Hassana Abu Firas, another refugee from Qusair, said: "What are we supposed to do? People are sitting in their homes and they are hitting us with tanks. Those who can flee, do. Those who can't will die sitting down."
Refugees said that the Syrian army had arrested many others trying to flee, while some said Lebanese forces had prevented others from crossing the border.
''We call on the Lebanese government and the Lebanese army to help us, to hide us, to hide our families, we don't
want anything we just want the Lebanese government to help the Syrian people, we appeal to them, we call on them to
help us, we call on the Muslims and the Arab governments to help us," Firas said.
Lebanese security officials say more than 10,000 Syrians have fled to Lebanon seeking refuge since March 2011. There are another 11,000 refugees in neighbouring Turkey.
As the Syrian military continued attacking opposition strongholds across the country, Turkish Prime Minister Recep Tayyip Erdogan urged Damascus on Tuesday to allow the immediate opening of humanitarian aid corridors.
"Humanitarian aid corridors must immediately be opened," Erdogan told a parliamentary meeting of his AKP party, urging the international community to put pressure on Damascus to allow the delivery of relief supplies to civilians.
Amid diplomatic efforts to end the crisis, the head of the Arab League said that Kofi Annan, the joint UN-Arab League special envoy to Syria, would travel to Damascus on March 10 for his first visit since being appointed to the post last month.
"Kofi Annan told me that Syria will receive him on March 10 and that he would arrive in Cairo on March 7," Nabil Elaraby, the Arab League secretary-general, said at the regional bloc's Cairo headquarters.
Annan will be accompanied by his deputy Nasser al-Kidwa, a former Palestinian foreign minister and UN envoy.
The UN humanitarian chief, Valerie Amos, separately announced that Syria had given her permission to visit the country from March 7-9, while China, which along with Russia has vetoed UN Security Council action against Syria, said that it would send a former ambassador to Damascus for talks with Syrian officials.