NATO Secretary General Jens Stoltenberg said today that North Korea's nuclear and missile programme represented a global threat and requires a global response.<br/><br/>In an interview with the BBC, he also refused to say whether an attack on the Pacific US territory of Guam would trigger the military alliance's collective defence clause. <br/><br/>Asked whether a strike against Guam would be covered under the clause that commits NATO members to come to the defence of each other, he said, he will not speculate about whether Article Five will be applied in such a situation.