The U.S. decision to focus on engagement with North Korea appears to have been a mistake, a senior fellow at a Washington-based think tank said after the reclusive state conducted four missile tests in a month.

U.S. President Joe Biden “chose engagement only,” said Anthony Ruggiero of the Foundation for Defense of Democracies. “That was his policy in 2021. He didn’t even sanction any of North Korea’s nuclear missile programs at all in 2021.”