According to recent reports, North Korea may be preparing to launch a missile or a satellite.
Satellite images suggest an increased activity around a site known as Sanumdong, where North Korea assembled most of its ballistic missiles and rockets.
It comes after reports earlier this week that North Korea’s main rocket launch site at Sohae had been rebuilt.
Last year, North Korea started to dismantle Sohae began but stopped as US talks stalled.
On March 8, President Donald Trump said he would be disappointed if North Korea was to resume weapons testing.
He said: “I would be surprised in a negative way if he did anything that was not per our understanding. But we’ll see what happens.
“I would be very disappointed if I saw testing.”
According to analysts, it is more likely at this stage that North Korea is preparing to launch a satellite rather than test a missile.
However, the US said earlier this week that this would still be inconsistent with the commitments Kim Jong-un has made to President Trump.
Large vehicles have been seen moving around Sanumdong, activity which has in the past indicated that Pyongyang was at least preparing to move some kind of missile or rocket to a launch area.
The satellite images were published by the public radio network NPR.
A much anticipated meeting between Donald Trump and Kim Jong-un in Hanoi last week ended without a deal over differences in how much North Korea was willing to limit its nuclear program before it was granted some sanction relief.
The Sohae launch facility at the Tongchang-ri site has been used for satellite launches and engine testing but never for ballistic missile launches.
This week’s satellite images, coming from several US think tanks and testimony from the South Korean intelligence service, appear to show rapid progress has been made in rebuilding structures on the rocket launch pad.
US National Security Adviser John Bolton has said North Korea could yet face more sanctions if there is no progress on denuclearization.
A historic first meeting between President Donald Trump and North Korean leader Kim Jong-un in 2018 in Singapore produced a vaguely worded agreement on “denuclearization” but little progress.