North Korea has been fanning World War 3 fears with its refusal to give up its nuclear arsenal.
Former Bill Clinton aide James Rubin warned North Korea could have further developed its nuclear weapons to make good on his promise to strike the United States.
He said: “I think more than what’s happened in the last few months is that the North Koreans now have something they never had before.
“They have the ability, probably, to take a nuclear weapon from Pyongyang all the way to any city in the United States.”
Mr Rubin said the development of North Korea’s nuclear capability was a new development in the “20-year” US policy of failure to handle the rogue nation.
He told CNBC: “Their new weapons-capability is the new part of this. Clinton, Bush, Obama and Trump: this is a 20-year failure of American foreign policy.
“But there are limits to what you can do in a country like that if you are not prepared to go to war. We’ve seen the reasons why you want to be cautious about war. We’ve squeezed them, we sanctioned them, we tried diplomacy, we tried agreements, they broke agreements. Everybody has failed but it’s a pretty tough problem.”
North Korea has refused to shut down its nuclear weapons development programme despite repeated warnings of economic repercussions from the international community.
The UN Security Council passed tougher sanctions against North Korea last month following its test of an intercontinental ballistic missile on November 29.
The sanctions are expected to cut North Korea’s foreign currency revenue from exports by approximately £185million ($250million) a year.
Despite leader Kim Jong-un having announced North Korea will participate in the Winter Olympics to defuse international tensions, US President Donald Trump deployed both nuclear supercarrier USS Carl Vinson and three nuclear-capable B-2 Spirit bombers to monitor North Korean activities during the games.
The USS Vinson is scheduled to arrive off the coast of the Korean Peninsula days before the opening ceremony, while the bombers touched down on the Andersen Aur Force Base in Guam on January 11, 2018.
The US overseas territory of Guam stands barely 2131 miles (3,430km) away from North Korea and was previously under threat of missile attacks from Pyongyang.