A leading academic has said Donald Trump's options of dealing with North Korea are running out after it called his bluff over a US deterrent.
The US President warned North Korea was drawing "fire and fury" if it continued to threaten America.
Hours later, North Korean state media said the country is considering a strike on the island of Guam, where the US maintains military bases.
In response to this, the US Department of Defense said they were capable of defending the island against any threat.
Dr Brian Klaas, a Global Politics Fellow at the London School of Economics, said the regime in Pyongyang had called out Donald Trump with this action.
He told Julia Hartley-Brewer: "The reality is Trump’s bluff just got called.
“When Assad used chemical weapons after Obama threatened a red line over it, it became apparent the US deterrent was a bluff. And this just happened in a matter of hours.
“Trump says if you threaten the US, we’ll attack you with fire and fury. Three hours later, Kim Jong-un says he’ll attack Guam and nothing happens.
“The President's left with two options - the first is to enforce his new red line and bomb North Korea - which would kill millions of people - or his deterrent is undercut completely because the threat is shown to be empty."
The academic said there was a real risk officials in North Korea could miscalculate over Trump's intentions.
He continued: "They could think Donald Trump’s saber-rattling might amount to an imminent strike, and attack as a result.
"That’s not to say Trump’s made this mess, but he’s made it worse with his rhetoric.
"A lot of wars in history have been down to miscalculation. That’s the real risk."