Powerful Gulf Arab countries pushed on Friday for more forceful intervention against Syrian President Bashar al-Assad and the United States warned he would have even more blood on his hands if he blocked aid to stricken civilian areas.

Speaking at a meeting of Western and Arab nations which sought to escalate pressure on Assad over his crackdown on 11 months of protests, Saudi Arabia's Foreign Minister Prince Saud al-Feisal said he supported arming the rebels.

I think it's an excellent idea, he said at the start of a meeting with U.S. Secretary of State Hillary Clinton, who warned Assad would pay a heavy price for the violence in Syria.

If the Assad regime refuses to allow this life-saving aid to reach civilians, it will have even more blood on its hands, Clinton said in prepared remarks for the meeting. So too will those nations that continue to protect and arm the regime.

In a political blow to Assad, the Palestinian Islamist group Hamas turned publically against their long-time ally on Friday.

I salute the heroic people of Syria who are striving for freedom democracy and reform, Hamas leader Ismail Haniyeh said.

The exiled political leadership of Hamas, based in Damascus for over a decade, quietly quit the Syrian capital recently but had tried to deny their absence had anything to do with the revolt.

Qatar's Foreign Minister Sheikh Hamad bin Jassim al-Thani said an Arab force should be created to impose peace and open humanitarian corridors in Syria.

He was addressing the first gathering of the Friends of Syria group, more than 50 countries who met against the backdrop of a surge in government attacks on the city of Homs and mounting world outrage over violence that has claimed thousands of lives during the uprising.

In Homs, Syrian government artillery fire killed five people in the city's Baba Amro district, opposition activists said, as the bombardment of opposition-held neighbourhoods entered its fourth week on Friday.

Baba Amro is being hit with 122mm artillery directed at it from surrounding villages. A father and his 14-year-old son were among those killed. They were trying to flee the shelling when shrapnel hit them in the street, Mohammad al-Homsi said.

The International Committee of the Red Cross said it was negotiating with Syrian officials and opposition forces in Homs for an evacuation of all sick and wounded in need of help.

French Foreign Minister Alain Juppe said the Red Cross and the governor of Homs were working to evacuate wounded foreign journalists stranded in the city.

SHOT THROUGH THE HEAD

Activists said Syrian security forces lined up and shot dead at least 18 people in a village in the central western Hama province. A video uploaded by activists showed people wrapping the bloodied bodies of children and at least four adults. Several had been shot through the head.

An updated draft declaration from the meeting called on Syria to immediately cease all violence to allow the United Nations access to Homs, and to let agencies deliver aid to civilians affected by the violence.

The Friends of Syria pledged, in the latest version of the draft seen by Reuters, to deliver humanitarian supplies within 48 hours if Syria's government stopped its assault on civilian areas and permitted access.

With moves for tough action against Syria in the U.N. Security Council stymied by Russian and Chinese vetoes and a lack of appetite for military action to end Assad's crackdown, delegates in Tunis have limited options.

The head of the main opposition Syrian National Council (SNC) expressed disappointment in the Tunis meeting. This conference does not meet the aspirations of the Syrian people, SNC chief Burhan Ghalioun told Reuters.

But in a sign the international community is seeking ways around the Security Council deadlock, U.N. Secretary General Ban Ki-moon said he would dispatch former U.N. chief Kofi Annan to Syria as a joint U.N.-Arab League envoy.

One Syrian opposition source said that although no country had yet decided to arm the rebels, foreign powers were turning a blind eye to weapons purchases by Syrian exiles smuggling in light arms, communications equipment and night vision goggles.

Syrian opposition supporters were also trying to bring anti-aircraft and anti-tank weapons to the Free Syrian Army rebels, and to get retired Syrian officers into the country to help coordinate military opposition to Assad.

HARSH REALITIES

The draft communique did not mention any foreign military intervention along the lines of the NATO bombing campaign that helped force out Libya's Muammar Gaddafi.

Instead, it called for further diplomatic pressure on Assad to step down and endorsed an Arab League plan that sees him handing power to a deputy as a prelude to elections.

The group will also commit to enforce sanctions aimed at pressuring Syrian authorities to halt violence, according to the draft declaration.

These include travel bans, asset freezes, a halt to purchases of Syrian oil, ceasing infrastructure investment and financial services relating to Syria, reducing diplomatic ties and preventing arms shipments to the Syrian government.

Juppe said the European Union, which has already imposed sanctions on Syrian officials, businesses and oil exports, would freeze assets of the Syrian Central Bank from Monday.

But the wording of the Tunis draft reflected a harsh reality: there is little the world can do to stop the violence as long as Russia and China, both of which declined invitations to the Tunis meeting, reject Security Council resolutions.

Another problem facing world powers is divisions within the Syrian opposition. While the Syrian National Council (SNC) attended the Tunis talks but the mainly Syrian-based National Coordination Body said it was not taking part.

British Foreign Secretary William Hague said London would now treat the SNC as a legitimate representative of the Syrian people. But the draft offered a weaker endorsement, proposing only that the SNC be recognised as a legitimate representative of Syrians seeking peaceful democratic change.

(Additional reporting by Dominic Evans in Beirut, Khaled Oweis in Amman, Lou Charbonneau at the United Nations, Arshad Mohammed and Myra MacDonald in London; Writing by Dominic Evans; Editing by Myra MacDonald)