President Joe Biden said on Monday he stood “squarely behind” his decision to withdraw U.S. troops from Afghanistan despite searing images of chaos in Kabul that exposed the limits of U.S. power and plunged him into the worst crisis of his presidency.

Breaking his silence on the U.S. pullout after scenes of bedlam dominated television news channels for days, Biden blamed the Taliban’s takeover in Afghanistan on Afghan political leaders who fled the country and the unwillingness of the U.S.-trained Afghan army to fight the militant group.

He warned Taliban leaders they would face “devastating force” should they interfere with the U.S. pullout. Biden was forced to send U.S. troop reinforcements to Kabul to ensure a safe withdrawal of American diplomatic personnel and civilians as well as Afghan citizens who worked with the United States and could face reprisals.

The panicked evacuation, coming weeks after Biden predicted the Taliban’s takeover in Afghanistan was not inevitable, has dented America’s image on the global stage just as Biden has sought to emphasize to world leaders that “America is back” after former President Donald Trump’s tumultuous four years.

The pullout has also raised fears that militant groups like al Qaeda could reconstitute under Taliban rule.

Biden, rejecting harsh criticism of his Afghan policy from Republican and Democratic lawmakers, some former generals and human rights groups, was resolute in defending his withdrawal from a 20-year war that endured through four presidencies.

I stand squarely behind my decision,” Biden said in a televised speech at the White House. “After 20 years I’ve learned the hard way that there was never a good time to withdraw U.S. forces. That’s why we’re still there.”

Biden said he found some of the scenes of chaos in Kabul “gut-wrenching” but that he did not start moving out evacuees sooner because Afghan President Ashraf Ghani did not want a mass exodus.