U.S. National Security Adviser John Bolton said Sunday that Secretary of State Mike Pompeo will make his fourth visit to North Korea soon.

In an interview with ABC's This Week, Bolton said that Pompeo has done extraordinary follow-up diplomacy after the Singapore meeting between the leaders of the U.S. and North Korea, adding that he expects Pompeo's diplomacy will resume in the near future. 

When asked about his criticism that North Korea has not taken steps to dismantle its nuclear program, Bolton stressed that it's important North Korea demonstrate seriousness. He reiterated that getting the North to denuclearize remains the “highest priority” for the U.S.

Bolton also said that he thinks North Korea could denuclearize within a year, adding the one year period is something "the North and South Koreans have already agreed to."