The Israeli author Amos Oz has joined six other intellectuals including the French Jewish philosopher Bernard-Henri Levy in calling on the UN Security Council to go further in its reaction to the government crackdowns in Syria.

In the letter the signatories, who also included Israeli novelist David Grossman and Salman Rushdie, said the 15 members of the Security Council should agree to adopt a resolution condemning President Bashar Assad's brutal crackdown.

The resolution has already been drafted by countries including Britain and France, but the letter stressed that "the outcome of this resolution" was in the hands of the Security Council.

"It qualifies the repression in Syria as a crime against humanity," they wrote. "It does not propose sanctions against Syria nor military intervention.

"It is limited to condemning the repression and clearing the path for investigations into the crimes against humanity. However limited, this resolution is necessary."

"It would be tragic and morally unacceptable if, because of the threat of an eventual veto or the occasional abstention here or there, this proposed resolution not be reviewed only to finish in the bin of abandonment," the letter said.

Earlier this week President Assad made a speech in which he said he understood the need for reform but accused foreign saboteurs of exploiting internal dissent.