Western powers acknowledged on Tuesday that ISIS has used chemical weapons "in one [case]," but they didn't allow the finding to detract from their condemnation of Syrian President Bashar Assad's military tactics.

"Syrian Arab Armed Forces were responsible for the use of toxic chemicals as weapons in three instances and ISIL/Da'esh in the use of chemical weapons in one," leaders at the G7 summit in Lucca, Italy, emphasized Tuesday. "We express our resolve to ensure that the use of chemical weapons remains a taboo."

The acknowledgment that ISIS has used such weapons might be used to amplify Russian government claims that the United States should not be certain that the Assad regime carried out the chemical weapons attack in Idlib province on April 4, which prompted President Trump's cruise missile attack days later. But the G-7 statement on Syrian chemical weapons paired that observation with previous findings that the Syrian military has been found to have used the weapons in three other cases, before concluding with condemnation of the latest gas attack.

"We are shocked by the reports of use of chemical weapons in an airstrike in the Khan Shaykhun area of southern Idlib on 4 April," the G-7 leaders said. "We condemn in the strongest terms any use of chemical weapons, including toxic chemicals as weapons, in Syria and express alarm over the continuing reports of civilians killed and injured by such use."

Russian President Vladimir Putin's team seemed to distance itself from Assad in the days immediately following the attack, but has returned to his defense diplomatically in the wake of U.S. strikes against the Syrian base. Putin accused the United States of planning to stage another chemical weapons attack that could be used as a pretext for attacking Assad once again.

"We have information that a similar provocation is being prepared ... in other parts of Syria including in the southern Damascus suburbs where they are planning to again plant some substance and accuse the Syrian authorities of using [chemical weapons]," Putin said Tuesday.

The Trump administration at first resisted, like the Obama administration before it, congressional and international calls for aggressive strikes against Assad. Secretary of State Rex Tillerson and other administration officials even made statements in the days before the attack implying they were abandoning Obama's pledge to call for Assad's ouster. "Our priority is no longer to sit and focus on getting Assad out," U.S. Ambassador to the United Nations Nikki Haley said in March.

But Assad's air force launched another chemical weapons attack against rebels within days, prompting a change in Trump's view of Syria. "It crossed a lot of lines for me," Trump said last week.

The U.S. Navy launched 59 Tomahawk cruise missiles at the Syrian airfield Thursday evening, setting off a diplomatic row with Russia days ahead of Tillerson's first visit to Moscow.

"Russia has failed to uphold the agreements that had been entered into under multiple UN Security Council resolutions," Tillerson told reporters during the G-7 Summit on Tuesday. "These agreements stipulated Russia as the guarantor of a Syria free of chemical weapons, that they would also locate, secure, and destroy all such armaments in Syria. ... It is unclear whether Russia failed to take this obligation seriously or Russia has been incompetent, but this distinction doesn't much matter to the dead. We can't let this happen again."