Syria is facing perpetual war as President Bashar Al Assad's forces fail to regain territory in Idlib despite a relentless campaign that is killing civilians and aid workers, UN officials said on Thursday.
In signs that belief in a peace process was falling apart, Britain said the Assad regime was committing war crimes and the US warned that stalling tactics showed Damascus was not serious about ending the conflict.
Syria's ambassador to the UN came under attack for repeatedly referring to humanitarian aid workers as terrorists”.
The remarks followed a stark assessment from UN special envoy for Syria Geir Pedersen, who said air strikes, shelling, rockets and mortar bombs in Idlib were killing innocents.
Three million people are trapped in the north-western province.
The attacks are often indiscriminate, Mr Pedersen told the Security Council, but “front lines have not shifted, at least not significantly”.
The Syrian government aims to drive Hayat Tahrir Al Sham, a coalition of rebels designated by the UN as a terrorist group, from Idlib. But fighting is not confined there.
“We must pursue a nationwide ceasefire,” Mr Pedersen said. “There are exchanges of fire and fatalities in northern rural Aleppo and continued signs of instability in the south-west.”
Najat Rochdi, the UN's senior humanitarian adviser to the special envoy, earlier said more than 300 civilians, many of them women and children, had been killed in the Idlib offensive, and 330,000 displaced from their homes.
The escalation is sending the wrong message to Syrian refugees, reinforcing their doubts about security and military conscription, Mr Pedersen said.
He appealed to Russia and Turkey, the guarantors of a failing de-escalation agreement in Idlib, to stabilise the situation.
“If that is achieved, we must then avoid the risk of a 'no war, no peace' scenario, with front lines mostly frozen but still periodic conflict and unrest,” he said.
Since becoming the special envoy six months ago, Mr Pedersen has restarted dialogue with Mr Al Assad's government and the country's exiled opposition, but fighting and bombing to reclaim rebel-held territory has raged, with Syria's main backer Russia helping the regime to control the skies.
Taking aim at Bashar Jaafari, the Syrian ambassador to the UN, US representative Jonathan Cohen said the Assad regime's attack on a bus carrying two White Helmets humanitarian workers on Wednesday showed promises it made were “repeatedly broken and disregarded”.
Mr Cohen said that in contrast to those risking their lives, Mr Jaafari was someone “who in the comfort of New York sat out the civil war in his country”.
Germany's ambassador to the UN, Christoph Heusgen, said: “What do you expect of the representative of a government that bombs its own civilians, that barrel bombs them?
"A government that puts its own people in prison, that continuously barrel bombs humanitarian aid workers. We are not that surprised.”
In response, Mr Jaafari again referred to humanitarian workers such as the White Helmets as terrorists.
Britain has consistently criticised Syria's attacks on aid workers, asking questions about Russia's role in Idlib.
The UK ambassador to the UN, Karen Pierce, said the Assad regime's "prevarications" on the political process meant it might be time "to try other routes".
Ms Pierce also repeated worries raised on Tuesday about Russian complicity in the possible use of UN-supplied coordinates helping the Syrian Air Force to target hospitals and schools.
“There are violations of the Geneva Conventions going on,” she told the council. “Those questions are still unanswered. I will return to them.”