Trump slams Russia, Iran behavior in Syria as a 'disgrace'

US President Donald Trump on Friday slammed as a "disgrace" the actions of the Syrian government and its Iranian and Russian backers, as the world struggles to stop a deadly assault on a rebel-held enclave near Damascus.

"I will say what Russia and what Iran and what Syria have done recently is a humanitarian disgrace," Trump told a news conference with Australian Prime Minister Malcolm Turnbull.

"What those three countries have done to those people is a disgrace."

Turnbull said Australia has been very generous in accepting refugees from Syria and says the Islamic State group's attempts to establish a caliphate has now "been smashed."

He added that Syria needed a political settlement reached by the people who live there.

Hundreds have been killed amid increased bombardments in recent days in rebel-controlled eastern suburbs of Damascus.

The death toll from the past week has climbed to more than 400 in Eastern Ghouta.

The US State Department has said Russia - whose air force is also striking Eastern Ghouta - has a "unique responsibility" for the mounting death toll in the besieged enclave.

The UN Security Council delayed a vote on demanding a 30-day ceasefire in Syria to Saturday at noon (1700 GMT) after hours of negotiations failed to yield agreement with Russia.

The council has been in talks on a draft resolution on the truce since February 9 as Syrian government forces have waged the fierce air campaign on Eastern Ghouta.

Negotiations have run into problems over a key provision of the text that specifies when the ceasefire will begin.

US Ambassador Nikki Haley has expressed dismay as the negotiations dragged out for another day on the pause that would allow for humanitarian aid deliveries and medical evacuations.

Negotiations have also stumbled over Russian demands that rebel groups fighting President Bashar al-Assad's forces comply with the truce.