North Korea threat top of agenda ahead of Trump talks with Chinese President Xi Jinping
Video report by ITV News Washington Correspondent Robert Moore
Intelligence agents in Britain and America believe it is likely that US President Donald Trump will be informed within the next two years that North Korea is within sight of developing a missile reliable enough to land a nuclear warhead in California.
Mr Trump has said that the United States will act alone to eliminate the nuclear threat from North Korea unless China puts more pressure on the regime.
He is due to meet the Chinese President Xi Jinping in a scheduled meeting in the US this week, during which Mr Trump said they will be discussing the issue of North Korea.
Five months after his election on an anti-China platform, Mr Trump appears to have set himself on a course for collision rather than conciliation with Xi, raising doubts as to whether the world's two biggest economies can find common ground.
Inconsistent views from the campaign trail - some favouring dialogue rather than confrontation with North Korea - make it unclear what Mr Trump will do or risk.
Analysts warn that a US pre-emptive strike could unleash a catastrophic chain of events.
Dr Patrick Cronin, Director of the Asia-Pacific Security Program for the Centre of New American Security in Washington DC, told ITV News: “The only way a pre-emptive strike makes sense is if you really have the intelligence that North Korea is about to launch a missile especially a nuclear missile into Seoul into Tokyo, into really kill people.
"If we knew that, and that's a big if, then a preemptive strike might make sense.
"But to try to strike the Yongbyon nuclear reactor or to try to strike two missile launch platforms on North Korea just because they're test firing an intercontinental missile would potentially trigger not only a tit for tat with North Korea that could escalate to the nuclear level but could bring the United States and China into a regional nuclear war.”
But tensions at Mr Trump's meeting with Xi Jinping at the billionaire's Mar-a-Lago resort in Florida go beyond what to do about North Korea.
The 70-year-old former real estate magnate, who had no foreign policy experience before entering the White House, has tweeted that it will be a "very difficult" meeting with the veteran Communist Party leader given Chinese trade practices which he says are killing US jobs.
Some White House aides believe Mr Trump's son-in-law and senior adviser Jared Kushner could be an influential moderating voice on how he handles Xi in their talks on Thursday and Friday.
Contacts between Kushner and China's US envoy helped smooth the way for the meeting, according to US officials.
But what worries the protocol-conscious Chinese more than policy clashes is the risk that the unpredictable Mr Trump could publicly embarrass Xi, after several foreign leaders experienced awkward moments with the new US president.