No breakthrough in talks

World and regional powers working to end the Syrian conflict vowed to bolster the country's shaky ceasefire yesterday but failed to set a new date for peace talks.

US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov put on their now customary joint appearance, but strains in the peace process were evident.

United Nations envoy Staffan de Mistura said he could not invite Bashar al-Assad's regime and the Syrian opposition back to peace talks until there is a "credible" ceasefire.

Kerry said the International Syrian Support Group (ISSG) had agreed there would be "consequences" for parties breaching the ceasefire and vowed to maintain pressure on Assad.

But Lavrov restated the Russian position that Assad's army is the best placed local faction to fight the Islamic State "terrorist" group and that Moscow would support it.

The evident divisions between ISSG co-chairs Russia and the United States have cast a pall on efforts to agree a framework under which Syria would "transition" away from Assad's rule.

And Kerry admitted the August 1 date set by the UN Security Council for agreement on the political framework was a "target" not a deadline, apparently softening the US stance.

Nevertheless, Kerry said the ISSG had agreed to strengthen its system for monitoring the ceasefire and that violators risked being expelled from the process.

Washington regularly accuses Assad's forces of violating the truce and of bombing civilians, whereas Russia accuses rebel factions of carrying out massacres.

Meanwhile, at least 50 fighters and two civilians were killed yesterday in clashes between rival anti-regime groups east of Syria's capital, the Syrian Observatory for Human Rights said.

The powerful Jaish al-Islam has been locked in clashes with rival factions led by al-Qaeda's Syrian affiliate in the opposition stronghold of Eastern Ghouta.

Observatory head Rami Abdel Rahman said nearly three weeks of fighting had killed more than 500 fighters and a dozen civilians.

In Aleppo, a regime air strike left at least seven civilians dead yesterday, among them a mother and her young daughter, according to the Observatory.

In Bdama in Idlib province in the northwest, large swathes of which are held by al-Qaeda's local affiliate Al-Nusra, regime strikes left eight civilians dead.

The Syrian war erupted in early 2011 after Assad's forces launched a brutal crackdown on anti-government protests, and has since claimed more than 270,000 lives.