A new report citing U.S. intelligence agencies says that North Korea has boosted its nuclear fuel production at multiple secret sites in recent months — despite leader Kim Jong Un's pledge to work toward denuclearization.

The report Friday by NBC News, citing more than a dozen American officials familiar with assessments by analysts at the CIA and other intelligence agencies, comes just weeks after U.S. President Donald Trump's landmark summit with Kim in Singapore. At the summit, Kim agreed in a vaguely worded joint statement to "work towards the complete denuclearization of the Korean Peninsula."

Trump has touted this as a major breakthrough with the nuclear-armed North after months of heated rhetoric and weapons tests, claiming in a tweet after the summit that there is "no longer a nuclear threat from North Korea."