For the fourth time in two weeks, North Korea has tested an increasingly sophisticated, hard-to-track missile system that could wipe out South Korean and Japanese cities — not to mention U.S. forces based in both countries. Yet Donald Trump says he's not worried.

The president and his team contend that diplomacy with North Korea remains on track, thanks in part to his personal rapport with leader Kim Jong Un. They say Kim has kept his word by holding off from testing a nuclear weapon or launching longer-range missiles capable of reaching the U.S. mainland.

The risks in that strategy are growing more worrisome as Kim seems increasingly intent on forcing Trump into concessions, critics say — and some members of the president's own administration privately agree. They argue that Trump is needlessly giving up leverage and may even encourage Kim to cross the U.S. red line on nuclear testing.