Secretary of State Marco Rubio says he is optimistic about the potential for a resumption in nuclear talks with Iran despite a shaky ceasefire in the war looking increasingly in doubt.

The U.S. military is waiting for clarity from the Pentagon following President Donald Trump's back-and-forth on troop levels in Europe, upending the lives of military personnel and potentially costing taxpayers millions of dollars, two U.S. defense officials told The Associated Press.