By Arshad Mohammed and Christian Lowe
TUNIS (Reuters) - Western and Arab nations mounted the biggest diplomatic push in weeks to end Syria's crackdown on the opposition on Friday, but the talk in a marble-lined Tunisian hotel risked being overtaken by the increasingly vicious armed conflict on the ground.
Foreign ministers from more than 50 countries in Tunis for the inaugural "Friends of Syria" meeting marshaled international condemnation of Syrian President Bashar al-Assad and ratcheted up the pressure on him to step down.
They met against the backdrop of a surge in government attacks on the city of Homs, an opposition stronghold, and mounting world outrage over violence that has killed thousands of people during the uprising.
U.S. Secretary of State warned Assad -- and his backers inside Syria and abroad -- that they will be held to account for the crackdown on opponents and what she described as a humanitarian catastrophe in Syria.
Addressing her comments to Russia and China, which vetoed tough action on Syria in the United Nations, she said: "They are setting themselves not only against the Syrian people but also the entire Arab awakening."
"It's quite distressing to see permanent members of the Security Council using their veto when people are being murdered - women, children, brave young men -- houses are being destroyed. It is just despicable."
"I am convinced Assad's days are numbered, but I regret that there will be more killing before he goes," she said.
Diplomatic moves though are hamstrung by the fact that, so far at least, there is little appetite for military intervention in Syria and attempts to ease Assad out via the United Nations Security Council have been stymied by Russian and Chinese vetoes.
Beijing and Moscow declined invitations to attend the meeting in Tunisia.
In a tacit acknowledgement that the scope for pressuring Assad through diplomacy is limited, some of the delegates at the conference -- especially Gulf states long opposed to Assad -- pressed for an international peacekeeping force in Syria and favored arming the Syrian rebels.
The Syrian opposition, meanwhile, appeared to be taking matters into its own hands, saying it was supplying weapons to rebels inside Syria while Western and other states turned a blind eye.
Saudi Arabia's Foreign Minister Prince Saud al-Faisal led the hawkish camp, saying that arming the Syrian rebels would be "an excellent idea."
Another hawk, Qatar's Sheikh Hamad bin Jassim al-Thani told the Tunis meeting an Arab force should be created to open and protect humanitarian corridors between opposition strongholds and Syria's neighbors.
LANGUAGE OF FORCE
Several representatives from the Syrian National Council (SNC), the main opposition group, said the conflict was increasingly entering a military dimension.
"We would have hoped that we could bring down the regime through completely peaceful means but the regime practiced violence and only understands the language of force," said SNC official Bassam Ishaak at the Tunis meeting.
"They came to power by force and they will only leave by force," he said.
Nevertheless, there was no mention in the "Friends of Syria" final communique of any plans for intervention, or arming the Syrian rebels.
Many Arab states which traditionally have had friendly ties with the Assad administration feel that further militarizing the crisis would tip Syria into a dangerous sectarian quagmire that could destabilize the whole region.
The Tunis meeting, in its final declaration, called on Assad to immediately cease all violence and allow access for humanitarian supplies. By late on Friday, the Red Cross said it had been able to reach Homs and was evacuating some of the wounded and sick women and children.
The "Friends of Syria" also committed to ratchet up sanctions on Syria. These would include travel bans on senior Syrian officials, freezing their assets, boycotting Syrian oil, suspending investments and preventing arms supplies to the government.
A diplomat attending the conference said the aim was to send a message to those who were wavering, especially the Syrian business community, that Assad was a lost cause.
"The point is to make the transition look more inevitable," said the diplomat.
The session in Tunis saw moves towards greater engagement with the often-fractious Syrian opposition.
Foreign governments see a coherent opposition movement that can represent all of Syria's different ethnic and religious groups - in essence, a government-in-waiting - as a vital precursor to pushing out Assad.
The communique identified the Syrian National Council as "a legitimate representative of Syrians seeking peaceful change." The meeting's chair, Tunisian Foreign Minister Rafik Abdessalem, said the group's next meeting in Turkey would grant a fuller endorsement.
"We have gone half the way and we will probably do the other half in Turkey," he said.
(Additional reporting by Dominic Evans in Beirut, Lin Noueihed, Tarek Amara, John Irish and John Hemming in Tunis; Writing by Christian Lowe; Editing by Myra MacDonald)