Boris Johnson has backed a diplomatic resolution to the North Korean crisis but says the US has an "absolute duty" to prepare "any option" in response to a nuclear threat.
He also urged US President Donald Trump to stick with the Iran nuclear deal.
Pyongyang's nuclear ambitions has stoked tensions in recent months leading to heated rhetoric between Mr Trump and North Korea's leader Kim Jong-un.
In a speech to the Chatham House foreign affairs think tank, Mr Johnson said: "No one wants any kind of military solution to the problem."
But he added that the US has to prepare to act when faced by a man "who not only threatens to reduce New York to 'ashes', but who stands on the verge of acquiring the power to make good on his threat".
Mr Johnson also praised US Secretary of State Rex Tillerson for keeping diplomatic options open with Pyongyang, despite Trump dismissing talk with the regime as a >"waste of time".
>"waste of time".
Source : http://www.itv.com/news/2017-10-23/boris-johnson-donald-trump-iran-north-korea/