A senior Saudi prince said on Friday that Arab states would not stay on the sidelines and allow the massacre of the Syrian people, and he suggested President Bashar al-Assad was unlikely to step down voluntarily.

Diplomatic efforts to resolve the crisis in Syria have stalled, with Assad rejecting a peace plan offered in early November by the 22-state Arab League.

That plan calls for government forces to be withdrawn to barracks and Arab observers to be allowed into Syria.

Former Saudi intelligence chief Prince Turki al-Faisal, seen as influential though no longer holding public office, said he believed the Arab League was not going to sit back and allow the continued massacre of the Syrian people.

Syria has been hit by United States and European Union economic sanctions and suspended from the Arab League for its crackdown on anti-Assad protesters.

Sanctions have been imposed. I think more measures will be undertaken in the near future, Prince Turki told a conference in Vienna.

Russia and China, however, have effectively blocked any similar move at the United Nations and Moscow is warning the West not to interfere in the affairs of its longtime Arab ally.

I think as the killing continues they will definitely come along with the rest of us and see the leadership of Syria has to give up and hopefully in a less bloody way than is now being contemplated, Turki said.

Asked whether there was any chance Saudi Arabia could help broker a possible power transfer deal as it did with Yemeni President Ali Abdullah Saleh, he said:

I do not think so because Ali Abdullah Saleh, while delaying and playing for time...he in the end signed the deal.

Getting Bashar al-Assad to sign on a deal has been the difficulty. The Arab League, the world community ... has offered Bashar al-Assad an opportunity to undertake a way out...He has refused and it is a pity because it means more bloodshed.

The United Nations says at least 4,000 people have been killed in Assad's crackdown on protests.

Syrian authorities blame the violence on armed groups and say 1,100 soldiers and police have been killed since the demonstrations erupted in March.

Turki said it was difficult to know how to proceed with Assad, who denies ordering his troops to kill peaceful demonstrators.

You have a president... who simply denies that there is anything wrong happening, he said, adding that this kind of leadership was unacceptable.

(Reporting by Michael Shields, Sylvia Westall and Fredrik Dahl; editing by Rosalind Russell)