Syrian President Bashar Assad has "no future" as a ruler of Syria, British Prime Minister Theresa May said in a break with President Trump's administration.

"There can be no future for Assad in a stable Syria which is representative of all the Syrian people, and I call on all the third parties involved to ensure that we have a transition away from Assad," May said Tuesday following reports of a chemical weapons attack that killed dozens of people in Syria.

That statement goes much further than the Trump administration's demurrals about Assad's future. Secretary of State Rex Tillerson said last week that "the longer-term status of President Assad will be decided by the Syrian people," a statement widely-regarded as an abandonment of former President Barack Obama's demand that he relinquish power. Assad rejected that demand, however, and Russian President Vladimir Putin helped Assad recapture a major rebel stronghold, placing his regime on firmer footing.

Like Tillerson, White House spokesman Sean Spicer seemed to indicate that the U.S. would not be pushing for Assad's removal.

"I think with respect to Assad, there is a political reality that we have to accept in terms of where we are right now," Spicer said Tuesday, elaborating on Tillerson's comment.

Because the gas attack took place just days after Tillerson's remarks, lawmakers on both sides of the aisle suggested that Assad felt emboldened to use such weapons by the change in U.S. policy. "Now that Donald Trump has put the world's superpower firmly on the sidelines, I fear what may come next for the Syrian people," New York Rep. Eliot Engel, the top Democrat on the House Foreign Affairs Committee, said Tuesday.

May indicated that at this point, it hasn't been proven that the Syrian regime was behind the chemical weapons attack. "We condemn the use of chemical weapons in all circumstances," she said. "If proven, this will be further evidence of the barbarism of the Syrian regime, and the UK has led international efforts to call to account the Syrian regime and Daesh for the use of chemical weapons and I would urge the Organization for the Prohibition of Chemical Weapons to investigate this incident as soon as possible."

The attack, which was reportedly an aerial bombardment near a rebel-held city, involved an initial gas attack and then a follow-up airstrike on medical facilities where victims were receiving treatment. "If it's what it looks like, it's clearly a war crime," a senior State Department official said Tuesday, according to the Daily Beast.