President Barack Obama says Russia and Iran must decide whether they want to prop up Syrian President Bashar Assad or "save the Syrian state" by finding a Syrian government that can be legitimate.
Obama is speaking during a meeting with Canadian Prime Minister Justin Trudeau.
He says it's unimaginable that Syria's civil war can be stopped without Assad leaving power. He says Assad "cannot regain legitimacy."
Obama says the goal of recent diplomatic efforts is to create space that could eventually lead to a "pivot" and political transition. He says a hoped-for cease-fire might not be observed by all parties but would create "pockets of calm."
Obama's comments come amid U.S. hopes that Russia may be warming to the idea of a future Syria that doesn't include Assad.