Russia has resisted the most recent US appeals to Moscow to persuade Syrian President Bashar al-Assad to quit and threaten Damascus with sanctions in hopes of ending Syria's civil war, the Russian newspaper Kommersant reported yesterday.

The report in the influential daily, which cited no named source, added to public signals that Russia is not prepared to push for Assad's exit despite efforts to distance itself from its longtime ally and buyer of Russian arms.

The report said Hillary had made the appeals to Russia in meetings with Lavrov in Dublin on Thursday - where they held talks with Brahimi - and in Cambodia last month.

Hillary also expressed concern that Assad's government might use chemical weapons against rebels fighting him, or that his allies could do so after the government falls, Kommersant said.

However, citing intelligence reports, US Defence Secretary Leon Panetta yesterday said Syria has not taken any new steps in recent days that signal a readiness to use its chemical weapons arsenal.

"At this point the intelligence has really kind of levelled off. We haven't seen anything new indicating any aggressive steps to move forward in that way," Panetta told reporters aboard his plane before landing in Kuwait.

Meanwhile, the United States yesterday blacklisted the Al-Nusrah Front, a rebel group in Syria linked to al-Qaeda in Iraq, and sanctioned its leaders.

In designating the group a foreign terrorist organization, the State Department said that while al-Nusrah portrayed itself as part of the legitimate Syrian opposition, "it is, in fact, an attempt by AQI to hijack the struggles of the Syrian people for its own malign purposes."

And the UN High Commissioner for Refugees said it had either registered or was in the process of registering 509,550 Syrians in Lebanon, Jordan, Iraq, Turkey and North Africa.