The Group of Seven major global powers were joined by Middle East allies on Tuesday in a push to isolate Syrian President Bashar al-Assad, hours before the U.S. secretary of state flies to Moscow, Assad's top backer.

Rex Tillerson says Russia must choose between aligning itself with the U.S. and like-minded countries or embracing Assad, Iran and the militant group Hezbollah.

Tillerson says it's unclear whether Russia failed to take seriously its obligations in Syria or it has been incompetent. But he says that distinction "doesn't much matter to the dead."

He says of the recent chemical attack: "We cannot let this happen again."

Tillerson says the U.S. sees no future role for Assad in Syria, but he says the U.S. isn't pre-supposing how Assad's departure will occur.

Tillerson is travelling Tuesday to Moscow. He says Russia can play a role in Syria's future, but that aligning with Assad won't serve Russia's long-term interests.

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U.S. Secretary of State Rex Tillerson talks with EU High Representative for Foreign Affairs Federica Mogherini during a meeting of the G7 for foreign ministers in Lucca, Italy. (Max Rossi/Reuters)

Chrystia Freeland, Canada's foreign affairs minister, said now is an opportunity for Russia to change course after the deadly gas attacks in Syria last week.

"Russia, as one of Assad's chief patrons, really needs to decide now — does it want to continue supporting a regime engaged in such heinous war crimes, or does it want to say, 'You know what, that was too much and now is a moment for us to take a different path,'" said Freeland.

"And let's hope that Tillerson, in his conversations with the Russians, is able to push that as a new political approach for Moscow."

She also said that Canada is "looking very carefully" at whether to impose more sanctions on Russia.

'No consensus' among G7 for new Russia sanctions

G7 foreign ministers sat down early on Tuesday with their counterparts from Turkey, Saudi Arabia, United Arab Emirates, Jordan and Qatar — all of whom oppose Assad's rule — to discuss the six-year-old civil war in Syria.

The inclusion of those countries is important because the U.S. strategy for Syria involves enlisting help from Mideast nations to ensure security and stability in Syria after the Islamic State group is defeated.

Meanwhile, pressure is building on Russian President Vladimir Putin to break ties with Assad, who stands accused of launching a nerve gas attack on a rebel-held town last week.

Italy G7 Foreign Ministers

Freeland, near left, and other foreign ministers and their staff sit at the table during the meeting of G7 foreign ministers in Lucca early Tuesday. (Riccardo Dalle Luche/ANSA via AP)

Italian Foreign Minister Angelino Alfano says there is "no consensus" among G7 countries for new sanctions on Russia over its support for Assad.

Alfano says the idea was raised at a meeting in Lucca, Italy, by British Foreign Secretary Boris Johnson. But Alfano said isolating Russia or pushing it into a corner "would be wrong."

He says "the G7's position is very clear — supporting the existing sanctions" against Russia over its military activities in Ukraine.

On Monday, British Prime Minister Theresa May spoke to U.S. President Donald Trump, with both agreeing that there was "a window of opportunity" to persuade Russia to break ties with Assad, May's office said.

Also on Monday, Britain and Canada said sanctions could be tightened on Moscow if it continued to back Assad. Later in the day, Trump spoke by phone with German Chancellor Angela Merkel about the U.S. strike last week and thanked her for her support.

"I think we have to show a united position and that in these negotiations we should do all we can to get Russia out of Assad's corner, at least to the point that they are ready to participate in finding a political solution," German Foreign Minister Sigmar Gabriel said on Monday. "It is the right moment to talk about this, how the international community, with Russia, Iran, Saudi Arabia, Europe, with the U.S., can drive forward a peace process for Syria and avoid further military escalation of the conflict."

Additional strikes

On Friday, the U.S. fired missiles at a Syrian airbase in retaliation for the alleged chemical weapons attack by Assad's government on civilians, including many children.

The U.S. is open to authorizing additional strikes on Syria if its government uses chemical weapons again or deploys barrel bombs in the country, the White House said on Monday.

The missile attack has increased expectations that Trump is ready to adopt a tougher stance with respect to Russia, and that he is ready to engage in world affairs instead of following the more isolationist stance he had previously taken.

Up until the chemical attack, Trump had said Washington would no longer act as the world's guardian, especially if it was not in the interest of the United States.

But on Monday, U.S. Secretary of State Rex Tillerson visited the site of a World War Two Nazi massacre in Italy and said Washington 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," Tillerson told reporters in Sant'Anna di Stazzema.

with files from CBC and the Associated Press