US Secretary of State John Kerry is to meet French and German ministers in London later as part of renewed attempts to broker peace in Syria.
On Saturday he met Russia’s Foreign Minister, Sergei Lavrov, along with representatives from other countries with stakes in the five-year conflict.
Nothing concrete came from that but both the US and Russia spoke of “ideas” emerging.
A ceasefire brokered last month collapsed after just a few days.
Since then Syrian forces, backed by Russia, have been bombing the city of Aleppo – the most high-profile battleground in the country’s civil war – in what Washington has called a war crime.
Aid agencies say a 72-hour ceasefire is urgently needed to allow supplies in and civilians out of devastated areas in the rebel-held and government-besieged east of the city, where 275,000 people live.
Mr Kerry’s talks with his French and German counterparts on Sunday will be hosted by the UK’s Foreign Secretary Boris Johnson.
No representatives of the Syrian government or opposition will be present.
The BBC’s Geneva correspondent Imogen Foulkes said Mr Kerry will not arrive in London with a detailed new peace plan for Syria, but instead with what he says are “fresh ideas”.
On Saturday Russia and the US were joined at peace talks in Lausanne, Switzerland, by countries who back opposing sides in the war.
Representatives from Saudi Arabia, Iran, and Turkey were there. Iranian troops are currently supporting Syrian forces, while Saudi Arabia is arming the opposition. Turkey is backing rebels who are currently advancing on Dabiq, a symbolic stronghold of the so-called Islamic State group.
After five hours in Switzerland negotiations broke up with no agreement on an end to the bombing of Aleppo or on aid for Syria’s besieged towns. But all the diplomats agreed to continue talking.
Mr Kerry suggested there could be a new road map for a ceasefire and a political transition for the country.
The talks in London follow an emergency debate in the House of Commons on Tuesday on the situation in Syria.
During the debate Mr Johnson said he would like to see a protest against bombings of Aleppo, which are being blamed on Russia, an ally of Syrian President Bashar al-Assad, outside the Russian embassy.
But Moscow, which denies the claims, accused him of “Russophobic hysteria”.
The United Nations has warned that eastern Aleppo, where an estimated 275,000 people still live, could face “total destruction” within two months.
Last week, Russia vetoed a UN Security Council resolution drafted by France calling for an end to the bombing in the city.
Syria conflict: US Secretary Kerry to visit London for talks}