The UN Security Council must make a "clear statement" to the Syrian government with a resolution condemning its crackdown of anti-regime protesters, British Foreign Secretary William Hague said Sunday.

As Syrian forces clashed with protesters in a flashpoint town and international outrage at the brutal action against demonstrators mounted, Hague said the prospects of passing a resolution were "on a knife-edge".

"I do believe it is time for the Security Council to make a clear statement of the kind that we're advocating," Hague told Sky News.

He said the resolution should call on Syria "to respond to legitimate grievances, to release prisoners of conscience, to open up access to the Internet and to cooperate with the UN High Commisioner for Human Rights".

Britain, France, Germany and Portugal drafted the resolution and have shown their frustration at opposition to it from some of the 15 Security Council members.

South Africa, Brazil and India have expressed strong reservations about the European resolution, which has been amended in a bid to win them over, and behind-the-scenes talks were continuing through the weekend.

Hague said it was "much more difficult" to get a UN resolution on Syria than it had been in the case of Libya, where a resolution authorising the use of force to protect civilians received wide backing.

"There is no prospect of getting through the UN a resolution such as the UN resolution 1973 on Libya," he said.

"In the case of Libya there was a clear call from the Arab League for action and that was a transformative intervention. There is no such call in the case of Syria."

Syria has strong links to Russia, and the inter-connections between the Syrian government and Lebanon -- the current Arab representative on the Security Council -- had made it "impossible for the Lebanese government to take a clear position on this", Hague said.

He also hit out at Iran, saying Syria was "undoubtedly being assisted by the Iranian government", through supplying "equipment" and advising on how to crush protests.

Iran's role was "an extraordinary example of hypocrisy in world affairs," Hague said.

"The prospects of passing a resolution are on a knife-edge at the moment," Hague said, adding he would speak to the Brazilian foreign minister on Sunday and had discussed the issues with his South African counterpart in recent days.

Hague also said it was "high time" that Syrian President Bashar al-Assad spoke to UN Secretary General Ban Ki-moon.

UN officials say Assad has been refusing to take telephone calls from Ban in recent days. Ban has become an outspoken critic of the Syrian leader since protests erupted in March in which at least 1,100 people have been killed.

Syrian state television said Sunday that troops had fought violent battles with "armed gangs" in the northern town of Jisr Al-Shughur, where 120 security personnel were killed this month.

The government advance sent thousands of people fleeing across the border into Turkey.