WASHINGTON -- President Donald Trump has taken the unusual step of tapping military leaders for high-level diplomacy, sending the top U.S. commander in the Middle East to talks over Iran’s nuclear program and positioning the Army secretary as a key negotiator on ending the Russia-Ukraine war.

The U.S. and Russia agreed Thursday to reestablish high-level military dialogue for the first time in more than four years in another sign of warming relations between the two countries since President Donald Trump returned to office and sought to end the war in Ukraine.