In a stunning admission, Lt Gen Jouas said the U.S. could face problems in getting reinforcements or new supplies to the Korean Peninsula, adding troops "may well find their bases subject to attack by conventional or chemical weapons, which will further delay their entry into the war".
Asked at news conference with Vietnam's president later Sunday if he could become friends with the North Korean leader, Trump replied it "might be a unusual thing to happen but it's certainly a possibility".
Asked if he could see himself being friends with Kim, Trump said: "That might be a unusual thing to happen but it's a possibility".
Trump's taunt of Kim came after the North Korean leader again called him a "dotard", a term describing an old person who is losing his mental faculties.
The president's remarks in a wide-ranging talk with reporters on Air Force One en route to Hanoi on Saturday and in his Sunday morning tweets have sharply punctured the careful messaging he and his aides had sought to deliver on a five-nation, 12-day trip through Asia.
In his tour of Asia, Trump has warned North Korea not to stretch USA patience, but also suggested the possibility of a diplomatic solution to the crisis.
He has tried to rally support to curb Pyongyang's rogue weapons programme during his trip, urging regional powers to stand united against North Korea.
"Every step you take down this dark path increases the peril you face".
North Korea's foreign ministry said of the comments, "Reckless remarks by an old lunatic like Trump will never scare us or stop our advance".
For the last months, the two leaders have been on two ends of a bitter war of words prompted in part by Pyongyang refusal to cease ballistic missile tests and the development of nuclear capabilities.
The president renewed his spat with North Korea as three US aircraft carriers were taking part in a military exercise in the Western Pacific in a show of strength to North Korea.
Trump hasn't always been a rhetorical foe of Kim.
The four-day exercise in the western Pacific involves USS Ronald Reagan, USS Nimitz and USS Theodore Roosevelt - as well as seven South Korean vessels, including three destroyers.
He said he asked the Russian leader if he interfered in the 2016 USA election and received assurances from Mr Putin that he "absolutely did not meddle". "The world has been provoked".