The top U.S. diplomat and NATO's chief say the military alliance is even more important now as a result of Britain's decision to leave the European Union.
U.S. Secretary of State John Kerry says he expects "an even stronger NATO going forward" as a result, stressing the alliance brings clarity at a time of uncertainty in Europe.
NATO Secretary-General Jens Stoltenberg said Britain's vote to pull out of the EU makes NATO more important now for defense and security coordination among European allies.
Meeting on June 27 at NATO headquarters, Kerry and Stoltenberg said NATO was on track for its July 8-9 summit in Warsaw.
Kerry will later meet EU foreign policy chief Federica Mogherini. He then travels to London to meet British Prime Minister David Cameron and Foreign Minister Philip Hammond.