Washington (CNN)The United States is "closer to a nuclear war with North Korea" than ever, Adm. Mike Mullen, a former chairman of the Joint Chiefs of Staff, said Sunday, adding that he does not "see the opportunities to solve this diplomatically at this particular point."

In an interview on ABC's "This Week," Mullen warned that President Donald Trump's provocative rhetoric aimed at North Korean leader Kim Jong Un likely indicates he would prefer to take a more aggressive approach to countering the rogue regime's rapidly evolving nuclear weapons program.

"I'm just more inclined to see over time that the rhetoric seems to be where the President is," Mullen said, adding that Defense Secretary James Mattis, national security adviser H.R. McMaster and White House chief of staff John Kelly have managed to deter Trump from following through on his threats of unleashing "fire and fury."

"My concern is how long that actually lasts," Mullen said, adding that, at some point, Trump may be inclined to ignore advice from his top national security advisers that runs counter to his own instincts.