Kim Jong-un

North Korea said Friday that leader Kim Jong Un called for stronger capability to cope with any foreign provocation.

Since April, Kim Jong Un and South Korean President Moon Jae-in exchanged personal letters several times.

The account comes from CNN's review of Bob Woodward's upcoming book, "Rage."

Small-scale exercises with South Korea have kept U.S. troops ready for conflict with North Korea, defense officials say.

The action followed reports that North Korea had warned of a possible missile launch or nuclear test for late December.

"There is no prospect of denuclearization until North Korea identifies its facilities and the location of its arsenal."

Pyongyang has stopped nuclear testing but officials say there is no evidence that nuclear stockpiles are decreasing.

"Both sides got some of what they wanted, but neither side got everything it was looking for."

One big outcome of the Singapore summit was commitment to accountability for the missing from the Korean War.

The U.S. is also prepared should North Korea resume test missile launches, officials said.