US: Talks with Russia on Syria 'on life support'

Two days after threatening to suspend talks with Russia on the crisis in Syria, the United States confirmed Friday that negotiations continue but insisted they are "on life support."

US Secretary of State John Kerry called Russia's Foreign Minister Sergei Lavrov for the third day in a row, but received no sign that Moscow is ready to halt the Syrian regime's assault on Aleppo.

On Thursday, amid much criticism at home and abroad that the threat to break off US-Russian bilateral talks on Syria was hollow, Kerry insisted that he was "on the verge" of ending them.

And that's where matters remained 24 hours later, State Department spokesman Mark Toner said, while introducing a new metaphor to describe how close the rival capitals are to a rupture.

"This is on life support, but it has not flatlined yet," he told reporters when asked why Kerry believes it is worthwhile to keep the diplomatic channel open while Russian jets pound Aleppo.

"It's egregious, it's horrific, it's in clear violation of international standards or norms, humanitarian norms and international law," Toner said.

And he agreed that "at a certain point" Washington would have to look again "to see if it becomes futile to continue to believe in a diplomatic process."

"That said, I just can't definitively say we're there at that point yet. We're very close but we're not there yet."

Earlier, Lavrov had hit out in an interview with the BBC, suggesting Washington may be trying to protect jihadist rebels from assault in order to later use them against Bashar al-Assad's regime.

Toner dismissed this charge out of hand. "It left me shaking my head, he said. "It's absurd."

A short-lived truce brokered by Moscow and Washington earlier this month fell apart as both sides blamed each other for its failure.

Moscow has since been accused of indiscriminately bombing rebel-held eastern Aleppo in support of an assault by Syrian government troops aiming capture all of the country's second city.