"I would be very disappointed if that were happening. It's a very early report. We're the one's that put it out, but I would be very, very disappointed in Chairman Kim," Trump said.
The reports come just days after Trump and North Korean leader Kim Jong-un failed to produce an agreement at their second summit in Hanoi.
US National Security Adviser John Bolton told Fox broadcaster on Tuesday that the United States would see if Pyongyang remained committed to abandoning its nuclear weapons program, warning that Washington might even consider "ramping up" economic sanctions on North Korea.
The second meeting between Trump and Kim in Hanoi last week ended abruptly when the US president walked away fro