North Korea appears to be building new ballistic missiles despite recent warming ties with the Trump administration and pledges to denuclearise, 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 quotes an official as saying it is unclear how far the work has gone.
Donald Trump met North Korea's Kim Jong-un in Singapore in June.
After the first meeting between sitting leaders from the two countries, the two men pledged to work towards denuclearisation. Mr Trump later said North Korea was "no longer a nuclear threat".
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.
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.
BBC - REUTERS