U.S. missile strikes on a Syrian air base last week in retaliation for an alleged chemical weapons attack on civilians in a rebel-held region by Assad's forces has raised expectations that President Donald Trump is ready to adopt a tougher-than-expected stance with Russia.
British Foreign Secretary Boris Johnson told reporters that Russia's reputation was being tarnished by its continued support of Assad and suggested, along with Canada, that sanctions could be tightened on Moscow if it continued to back Assad.
It was unclear how far U.S. Secretary of State Rex Tillerson was prepared to push the Russian leadership when he travels to Moscow on Tuesday at the end of the two-day G7 gathering in the Tuscan city of Lucca.
"What we're trying to do is to give Rex Tillerson the clearest possible mandate from us as the West, the U.K., all our allies here, to say to the Russians 'this is your choice: stick with that guy, stick with that tyrant, or work with us to find a better solution'," Johnson said after meeting Tillerson.
Russia has rejected accusations that Assad used chemical arms against his own people and has said it will not cut its ties with the Syrian president, who has been locked in a six-year-old civil war that has devastated his country.
"Returning to pseudo-attempts to resolve the crisis by repeating mantras that Assad must step down cannot help sort things out," Dmitry Peskov, the spokesman for Russian President Vladimir Putin, said on Monday.
"CRIMES AGAINST INNOCENTS"
Tillerson himself said at the weekend that the main priority for the United States was the defeat of one of Assad's main foes, the Islamic State militant movement.
Those comments left U.S. allies wondering whether the April 7 missile attack was a one-off event.
On Monday, the former oilman-turned-diplomat visited the site of a World War Two Nazi massacre in Italy and said the United States would never let such abuses go unchallenged.
"We rededicate ourselves to holding to account any and all who commit crimes against the innocents anywhere in the world," he told reporters in Sant'Anna di Stazzema.
Looking to build their case against Assad, Italy has invited the foreign ministers from Turkey, Saudi Arabia, United Arab Emirates, Jordan and Qatar to sit down with the G7 group on Tuesday morning to discuss Syria. All oppose Assad's rule.
The foreign ministers' discussions will prepare the way for a G7 leaders' summit in Sicily at the end of May, which looks set to be Trump's first overseas trip since becoming president.
Besides Syria, the ministers will talk about growing tensions with North Korea, as the United States moves a navy strike group near the Korean peninsula amid concerns over Pyongyang's nuclear ambitions.
They will also debate Libya. Italy is hoping for vocal support for a United Nations-backed government in Tripoli which has struggled to establish its authority even in the city, let alone in the rest of the violence-plagued north African country.
The Trump administration has not yet defined a clear policy and Rome fears Washington may fall into step with Egypt and Russia, which both support general Khalifa Haftar, a powerful figure in eastern Libya.
The struggle against terrorism, relations with Iran and instability in Ukraine is also on the agenda, with the meeting expected to finish by midday on Tuesday.
(Reporting by Crispian Balmer and Steve Scherer; Editing by Tom Heneghan)