"Despite a reduction in tensions along the demilitarized zone and a cessation of strategic provocations coupled with public statements of intent to denuclearize, little to no verifiable change has occurred to North Korea's military capabilities," General Robert Abrams testified to lawmakers.

"These capabilities continue to hold the United States, South Korea and our regional allies at risk."

Abrams said he believed it necessary to maintain a "postured and ready force to deter any possible aggressive actions."

Asked about signs of military activity reported in news outlets -- triggering fear North Korea is preparing missile or rocket tests -- the general said he could not comment in open session.

"Their activity that we have observed is inconsistent with denuclearization," said Abrams.

President Donald Trump and North Korean leader Kim Jong Un met at an unprecedented summit last June in Singapore, after which Kim agreed to work toward denuclearization of the Korean peninsula.

But since then negotiations to turn that vague pledge into something concrete have failed to yield progress, and a second meeting between the two men in February in Vietnam ended abruptly and without agreement.

Trump has been criticized for lending legitimacy to the North Korean dictator, whose regime has an atrocious human rights record.

"Just landed - a long trip, but everybody can now feel much safer than the day I took office," he tweeted after Singapore.

"There is no longer a Nuclear Threat from North Korea. Meeting with Kim Jong Un was an interesting and very positive experience."

The United States says it will not accept a gradual denuclearization of North Korea but rather wants it to be swift and total, in exchange for lifting sanctions.