A new intelligence report says North Korea has increased its production of enriched uranium for nuclear weapons at secret sites in recent months, contrary to Donald Trump’s claims that it was “no longer a nuclear threat”.

According to a new intelligence assessment, satellite images show rapid improvements being made to a North Korean nuclear research facility at Yongbyon.  The developments will make it harder for Trump to claim that his summit with Kim Jong-un in Singapore was a success.

Neither of the concessions the US president claimed Kim Jong-un  had delivered – the destruction of a missile engine testing site, and the repatriation of the remains of US soldiers killed in the Korean war – has materialised so far.

Meanwhile Trump has already made a significant US concession: suspending joint military exercises with South Korea that had been due to start in August.

The US secretary of state, Mike Pompeo, is reported to be planning a trip to Pyongyang in early July to continue negotiations with the North Korean government, in the hope of persuading Pyongyang  to make specific commitments on nuclear disarmament.

Over the past seven months the North Koreans have conducted no new missile or nuclear tests. But NBC quoted a US official briefed on the latest intelligence as saying that uranium enrichment had been stepped up.

“There’s no evidence that they are decreasing stockpiles, or that they have stopped their production,” the official said. “There is absolutely unequivocal evidence that they are trying to deceive the US.”

US intelligence believes the North Koreans have established a uranium enrichment plant in at least one secret site apart from Yongbyon complex.  The joint statement signed by Trump and Kim in Singapore was vaguely worded. Kim promised “complete denuclearisation” but that has been Pyongyang’s theoretical policy since 1992, and North Korea  interprets it to mean a long-term mutual process in which the US would also disarm.