UNITED NATIONS: UN leader Ban Ki-moon on Friday demanded that the UN Security Council act on the Syria conflict, warning that any failure would be giving “a license for further massacres”.

Ban joined with UN-Arab League envoy Kofi Annan to express outrage at the mass killings in the Syrian village of Treimsa and to make an “urgent call” for pressure on President Bashar al-Assad. Annan said Security Council resolutions had been “flouted”.

“I call upon all member States to take collective and decisive action to immediately and fully stop the tragedy unfolding in Syria. Inaction becomes a license for further massacres,” Ban said in a hard-hitting statement aimed at the council.

The massacre of at least 150 people in Treimsa has added new urgency to deadlocked Security Council negotiations on a Syria resolution. Russia has rejected western demands for non-military sanctions to be threatened to back Annan's peace efforts.

Ban expressed outrage at the “horrific” killings in Treimsa on Thursday, which he said cast “serious doubt” on Assad's commitment to an international peace plan.

The UN leader strongly condemned “the indiscriminate use of heavy artillery and shelling of populated areas, including by firing from helicopters.”

Annan said in a letter to the Security Council that the use of artillery, tanks and helicopters was “a violation of the Syrian government's obligations and commitment to cease the use of heavy weapons in population centers.”

Tragically, we now have another grim reminder that the council's resolutions continue to be flouted,” Annan said in the letter.

The council passed two resolutions in April which set up the UN Supervision Mission in Syria (UNSMIS) and demanded that Assad carry out the six-point peace plan he agreed with Annan. The agreement included a halt to the use of heavy weapons.

Annan reaffirmed his call for the council to “send a message to all that there will be consequences for non-compliance” with his plan.

“This is imperative and could not be more urgent in the light of unfolding events,” he added.

UN envoys held more talks Friday in a bid to break their deadlock on a Security Council resolution to renew the UN mission. A vote must be held by July 20 when the mission's 90-day mandate runs out.

A resolution proposed by Britain, France, United States, Germany and Portugal would give Assad 10 days to stop the use of heavy weapons, in line with the Annan plan, or face sanctions.

The western nations only want to give UNSMIS a new 45-day mandate.

Russia's rival resolution would renew UNSMIS for 90 days but makes no mention of international measures. The Russian government has said sanctions are “unacceptable” and would not be allowed.

US Secretary of State Hillary Clinton led the west's calls for Russia to agree new action following the latest massacre.

She said the reported use of artillery, tanks, and helicopters were “indisputable evidence that the regime deliberately murdered innocent civilians.”

The Security Council should put its full weight behind the Annan plan for an immediate ceasefire and a political transition and make clear to the Syrian regime that there will be consequences for non-compliance,” Clinton said.

“History will judge this Council. Its members must ask themselves whether continuing to allow the Assad regime to commit unspeakable violence against its own people is the legacy they want to leave,” Clinton added.