His warning follows a North Korean state-controlled newspaper on Sunday accusing the U.S. of "double-dealing" and "hatching a criminal plot" against Pyongyang after Washington abruptly canceled a visit by Secretary of State Mike Pompeo.
The decision to cancel Pompeo's trip appeared to have been made abruptly, coming just a day after Pompeo announced it would happen.
Since Trump's summit with North Korea dictator Kim Jong Un, the U.S. has called off its military exercises with South Korea while China and Russia have softened pressure on North Korea.
"We are worse off than where we were when the summit happened because, in the meantime, China and Russia have alleviated sanctions pressure on North Korea. We've also unilaterally canceled our military exercises with South Korea with our own president even labeling these exercises provocative which certainly unnerved Japan," said Sean King, senior vice president at public policy and business development firm Park Strategies.
Even during the June summit, King said, both parties seemed to have misunderstood to what the other was agreeing.
"Trump thinks he (Kim) said he will give up his nukes and then we will work toward some kind of peace deal. But in Kim's mind, it is the end of the U.S.-South Korea alliance first and then maybe he will denuclearize," King said.
King suggested that part of the problem was a difference of opinion about strategy within the White House.
"You have a professional staff that is talking a hard line, and the president feels he could do his own deal based on personal chemistry. It is like we have two parallel administrations and North Korea is trying to exploit that," King said.
Moving forward, King said the U.S. should take a tougher stance against China and North Korea if denuclearization is a priority.
— Reuters and CNBC's Christina Wilkie contributed to this report