South Korean military exercises this weekend.
The comments came as Asian foreign ministers met in Vietnam for a regional security forum.
The forum has been dominated by the crisis resulting from North Korea's alleged sinking of a South Korean warship in March.
The US has accused Pyongyang of 'provocative' behaviour and on Wednesday announced new sanctions.
North Korea's delegation spokesman at the Association of South East Asian Nations (Asean) Regional Forum (ARF) in Hanoi said the military exercises - which begin on Sunday - were an example of 19th century 'gunboat diplomacy'.
'It is a new century and Asian countries are in need of peace and development, and DPRK [North Korea] is also moving to that end,' said Ri Tong-il.
He said the exercises went beyond defensive training and would involve 'sophisticated weapon equipment'.
'It is a threat to the Korean peninsula and the region of Asia as a whole. And the DPRK's position is clear: there will be a physical response to the threat imposed by the United States militarily.'" More...