Yet the Republican presidential front-runner outlined no strategy for how he'd make the United States at the same time a "consistent" and "unpredictable" force in the world. And he didn't appear to allay the concerns of U.S. and international critics - Republicans at home as well as Democrats - who see him as unfit for the responsibilities of commander in chief.

"'America first' will be the major and overriding theme of my administration," Trump declared, echoing motifs from his campaign that is now close to sealing the GOP nomination.

Delivering his lines in a more sober, restrained manner than usual to cast himself as presidential material, the billionaire businessman and reality TV star toned down or omitted several of his most explosive - and oft-repeated - barbs. He made no reference to forcing Mexico to pay for a wall across the nation's Southern border. He also didn't revisit the idea of allowing Japan, South Korea, Saudi Arabia or any other country to develop nuclear weapons for self-defense purposes.