President Donald Trump said he received a letter from Kim Jong Un on Thursday in which the North Korean leader complained about war games conducted jointly by the U.S. and South Korean militaries.

“He wasn’t happy with the testing,” Trump said Friday as he departed the White House for a fundraiser in the Hamptons. “We’ll see how it all works out.”

National Security Adviser John Bolton has said current U.S.-South Korean drills are “largely computer-driven,” with fewer troops maneuvering than in exercises that Trump ordered halted.

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.

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