A group of former Republican-appointed national security officials, including several now at leading U.S. law firms, called on GOP leaders Monday to urge Donald Trump to concede the 2020 election, saying his refusal to accept his loss to President-elect Joe Biden raises “significant risks.”

In an open letter, the former officials said Trump’s intransigence has not only delayed the transition, presenting unprecedented challenges to Biden as he prepares to take office, but also undermines democracy and risks causing “long-term damage to our institutions.”