The US and Britain are considering imposing sanctions against the Assad regime and Russia over the crisis in Aleppo.
The US Secretary of State, John Kerry, met with French, Italian and German ministers today as part of a renewed push to broker peace in the worn-torn country.
The talks were hosted by British Foreign Secretary Boris Johnson, but no representatives of the Syrian government or opposition were in attendance.
Mr Johnson said Syrian President Bashar al Assad and the Russians cannot win the war in Syria and warned that “no option is in principle off the table” after suggesting earlier in the week that western forces may be willing to consider a military intervention in the conflict.
He said western powers are considering imposing economic sanctions against both regimes over the five-year siege of Aleppo.
“I am not going to pretend that there is some magic solution for this appalling slaughter because the real answer, I’m afraid, lies with those who are perpetrating it ... The Assad regime and the Russians,” he said.
Mr Kerry said what is happening in Aleppo constitutes "crimes against humanity" but said he sees no appetite in Europe for "people to go to war".
"I don't see the parliaments of European countries ready to declare war; I don't see a lot of countries deciding that that is the better solution here,” he said.
"So we are pursuing diplomacy because those are the tools that we have and we're trying to find a way forward under those circumstances."
Mr Johnson said the west needs use diplomatic tools to deal with the crisis.
“Be in no doubt that these so-called military options are extremely difficult and there is, to put it mildly, a lack of political appetite in most European capitals and certainly in the West for that kind of solution at present,” he said.
"So we've got to work with the tools we have - the tools we have are diplomatic.
"I think the most powerful weapon we have at the moment is our ability to make president Putin and the Russians feel the consequences of what they are doing."
Today's meeting came after Mr Kerry's Saturday talks with his Russian counterpart Sergey Lavrov in Switzerland ended without any formal agreement.
The talks included representatives from Iran, Iraq, Qatar, Jordan, Saudi Arabia, Egypt and Turkey.
Mr Kerry said that there had been consensus on some key concepts adding that parties would contact each other again on Monday.
"The way it wrapped up was to have several ideas that need to be quickly followed up," he said.
A ceasefire agreed last month collapsed after just a few days and Syrian regime forces - backed by Russia - are continuing to pound rebel-held areas of Aleppo.
Washington has called the military action a war crime.
Air Chief Marshal Michael Graydon - a former chief of the air staff in the British army - said agreement from Syria and Russia is essential in order to deal with the growing humanitarian crisis:
Aid agencies say a 72-hour ceasefire is urgently needed to allow supplies in and civilians out of devastated areas in the government-besieged east of the city, where 275,000 people live.
Humanitarian organisation Médecins Sans Frontières said the area’s struggling healthcare system suffered its worst day since the collapse of the ceasefire on Friday with confirmed attacks on four hospitals and on an ambulance - leaving at least two doctors injured and one ambulance driver dead.
At least 62 people died and 467 people - including 98 children - were wounded between October 11th and 13th according to reports obtained from the Directorate of Health and the forensic centre of east Aleppo.
The United Nations has warned that eastern Aleppo could face "total destruction" by Christmas if there is no end to the bombardment.
Last week, Russia vetoed a UN Security Council resolution drafted by France calling for an end to the bombing in the city.
