North Korea is threatening a "physical response" to scheduled U.S.-South Korean naval maneuvers beginning Sunday in the Sea of Japan.
The outburst Friday was the latest shot in a war of words that eclipsed other issues at the ASEAN Regional Forum in Hanoi.
On Friday U.S. Secretary of State Hillary Clinton described North Korea as an "isolated and belligerent" regime engaged in a "campaign of provocative, dangerous behavior." Earlier this week, she announced new economic sanctions against Pyongyang.
North Korean spokesman Ri Tong Il responded furiously at the 27-member forum, describing the planned exercise as a threat to his nation's sovereignty and a reminder of 19th century gunboat diplomacy.
He said, "There will be a military response against the threat imposed by the United States militarily."