The search for a unified approach to the Syria conflict after last week’s suspected chemical attack looks set to dominate talks between the G7 group of leading nations in Italy on Monday.
Foreign ministers will focus on how to pressure Russia to distance itself from Syrian President Bashar al-Assad.
Allies will also be seeking clarity from the US on its Syria policy, after some apparently mixed messages.
US Secretary of State Rex Tillerson strongly criticised Russia on Sunday.
He said it had failed to prevent Syria from carrying out a chemical attack on the rebel-held town of Khan Sheikhoun last Wednesday which left 89 people dead.
But he also clarified there had been “no change to our military posture” in Syria following a retaliatory US strike against a Syrian airbase, and that Washington’s “first priority” in Syria was to defeat the Islamic State terror group.
Those comments came a day after the US ambassador to the United Nations said there was no way to stabilise Syria with Mr Assad as president.
“In no way do we see peace in that area with Assad as the head of the Syrian government,” Nikki Haley told NBC’s “Meet the Press”.
However, she had said last week that Mr Assad’s removal was no longer a US priority.
What are the options for pressuring Russia?
BBC diplomatic correspondent James Robbins says the next two days will be dominated by a collective search for arguments to persuade President Vladimir Putin he must now end Russia’s military support for President Assad and help accelerate a negotiated political transition.
UK Foreign Secretary Boris Johnson is expected to press the case for new sanctions against Russia if Moscow does not give ground.
Russia is already under a raft of sanctions imposed by the US and EU in response to the annexation of Crimea and the crisis in eastern Ukraine. These target Russian individuals and businesses, and key sectors of the Russian economy closely connected to the ruling elite.
Mr Tillerson wants to go on from the G7 talks to Moscow, able to confront the Russians with a strong set of demands backed by key US allies.