North Korea appears to be building new ballistic missiles despite recent warming ties with the Trump administration, media reports say.
Unnamed US officials told the Washington Post that spy satellites had spotted continuing activity at a site that has produced ballistic missiles.
Reuters news agency quotes an official as saying it is unclear how far the work has gone.
But Mr Trump was criticised at home for making concessions without securing any firm commitment from Mr Kim to end the nuclear and missile programmes.
What do the latest reports say?
On Monday, the Washington Post newspaper quoted officials as saying North Korea appeared to be building one or two new liquid-fuelled intercontinental ballistic missiles (ICBMs) at the Sanumdong facility near the capital, Pyongyang.
Reuters also added that satellite imaging showed vehicles moving in and out of the facility, but not the extent of any missile construction.
What are experts saying about this?
These are not the first reports that North Korea may be continuing its weapons programme, casting doubt on the real impact of the summit in Singapore.
Satellite imagery of the Sanumdong facility shows that the site is “active”, Jeffrey Lewis, a nuclear expert at the Middlebury Institute of International Studies (MIIS) told the Washington Post.