North Korea has taken a major step forward in realizing its goal of becoming a nuclear power, according to a confidential US intelligence assessment that concludes Pyongyang has developed a nuclear warhead capable of fitting inside its missiles. 
The Washington Post first reported details of the assessment on Tuesday just hours after North Korea threatened 'physical action' in response to punitive sanctions unanimously passed by the United Nations Security Council over the weekend, CNN reported. 
"The IC [intelligence community] assesses North Korea has produced nuclear weapons for ballistic missile delivery, to include delivery by ICBM-class missiles," the assessment stated. 

Source : Mena