(CNN) -- Foreign ministers of leading US allies were meeting Monday amid mixed signals from the Trump administration on the future of Syrian President President Bashar al-Assad.
At a summit in Italy, foreign ministers of the G7 group of industrialized nations were expected to seek clarity from US Secretary of State Rex Tillerson on whether the US is now committed to deposing the Assad regime.
At the weekend, US ambassador to the UN Nikki Haley suggested regime change in Syria was inevitable in the wake of last week's chemical weapons attack that was widely blamed on the Assad regime.
Haley told CNN's "State of the Union" that removing Assad was now a US priority. "If you look at his actions, if you look at the situation, it's going to be hard to see a government that's peaceful and stable with Assad," she said.
But Tillerson was more equivocal, saying that the priority was the defeat of ISIS. Asked on CBS's "Face the Nation" whether deposing Assad was a priority, he replied: "I think the president has been quite clear. First and foremost, we must defeat ISIS." He went on to say that the Syrian people would determine the future of Assad.
Senior Trump administration officials stepped up their rhetoric against Russia at the weekend, ahead of a meeting between Tillerson and his Russian counterpart Sergey Lavrov in Moscow later this week.
Tillerson said Russia's support of the Syrian regime made it complicit in the Assad's actions.
"I hope Russia is thinking carefully about its continued alliance with Bashar al-Assad, because every time one of these horrific attacks occurs, it draws Russia closer into some level of responsibility," Tillerson said on ABC's "This Week with George Stephanopoulos" on Sunday.
Haley said Tillerson would put pressure on Moscow over its support for Assad. "There's a lot of answers that need to come from Russia. I think that's why it's good that Secretary Tillerson is going to Russia this next week. And I think that there will be a lot of answers that come out of that meeting," she told CNN's "State of the Union" on Sunday.
"We're calling (Russia and Iran) out," Haley added. "But I don't think anything is off the table at this point. I think what you're going to see is strong leadership. You're going to continue to see the United States act when we need to act."
Foreign ministers of the G7 group of nations, which include the US, Japan, Britain and Germany, were gathering in Lucca, Italy, on Monday, where Syria was likley to dominate the agenda. It is the first meeting of US allies since President Donald Trump ordered the bombardment on the Shayrat airbase in western Syria last week.
The US fired 59 Tomahawk missiles at the Shayrat Airfield in Syria Friday, which housed the warplanes the US believes were used in last week's chemical weapons attack on civilians.
Russian President Vladimir Putin discussed the strike on the phone with Iranian President Hassan Rouhani Sunday. Both leaders agreed on the "inadmissibility" of US action against a sovereign state.
In a statement issued by the Kremlin, Russia and Iran both called for an "objective, unbiased" investigation into the chemical attack that provoked the strikes.
Warning from Iran
On Monday, Rouhani warned the US not to carry out any more strikes against Syria. "Repeating this action can be very dangerous for the region," he said.
Tillerson and Lavrov discussed the missile strike in a phone call Saturday. According to a statement issued by Russia's Foreign Ministry, Lavrov said US statements that the Syrian government used chemical weapons "do not correspond with reality."
"Lavrov stressed that an attack on a country whose government is fighting terrorism only plays into the hands of extremists creates additional threats to regional and global security," the statement said.
Tillerson said Russia should do more to meet commitments it made in 2013 to guarantee the destruction of Syria's chemical weapons. "That will part of the discussions when I visit Moscow next week is to call upon Foreign Minister Lavrov and the Russian government to fulfill the obligation it made to the international community when it agreed to be the guarantor of the elimination of the chemical weapons," he told ABC on Sunday.
"And why Russia has not been able to achieve that is unclear to me. I don't draw conclusions of complicity at all, but clearly they've been incompetent and perhaps they've just simply been out-maneuvered by the Syrians."
US flip-flops on Syria
The Trump administration has dramatically reversed its position on Syria in the past week.
In her CNN interview Sunday, Haley suggested that a change of government in the war-ravaged nation was inevitable, and said removing Assad was now a US priority.
"If you look at his actions, if you look at the situation, it's going to be hard to see a government that's peaceful and stable with Assad," she said.
"Regime change is something that we think is going to happen because all of the parties are going to see that Assad is not the leader that needs to be taking place for Syria."
Haley's comments were a significant departure from President Donald Trump's previous stance on Assad's future -- before to his election victory in November, he said fighting Assad and ISIS simultaneously was "idiocy."
Only five days before the chemical attack, Haley said removing Assad was not a priority.
"Our priority is no longer to sit and focus on getting Assad out," Haley had told reporters on March 30. On the same day, Tillerson said on a trip to Turkey that the "longer-term status of Assad would be decided by the Syrian people."
CNN's Radina Gigova and Darya Tarasova in Moscow, Hamdi Alkhshali and Merieme Arif in Atlanta and Bijan Hosseini in Abu Dhabi all contributed to this report.
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