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Pak Rim-su, chief delegate of the North Korean military mission to the inter-Korean truce village of Panmunjom, gave the message by phone to Gen. James Thurman, the commander of the US Forces Korea, KCNA news agency said.
It came amid escalating tension on the divided Korean peninsula after the North's third nuclear test earlier this month, in defiance of U.N. resolutions, drew harsh international condemnation.
A direct message from the North's Panmunjom mission to the US commander is rare.
North and South Korea are technically still at war after their 1950-53 conflict ended in a truce, not a peace treaty.
The US-South Korean Combined Forces Command is holding an annual computer-based simulation war drill, Key Resolve, from March 11 to 25, involving 10,000 South Korean and 3,500 US troops.
The command also plans to hold Foal Eagle joint military exercises involving land, sea and air manoeuvres. About 200,000 Korean troops and 10,000 US forces are expected to be mobilized for the two month-long exercise which starts on March 1.
"If your side ignites a war of aggression by staging the reckless joint military exercises...at this dangerous time, from that moment your fate will be hung by a thread with every hour," Pak was quoted as saying.
"You had better bear in mind that those igniting a war are destined to meet a miserable destruction."
Washington and Seoul regularly hold military exercises which they say are purely defensive. North Korea, which has stepped up its bellicose threats towards the United States and South Korea in recent months, sees them as rehearsals for invasion.
North Korea threatened South Korea with "final destruction" during a debate at the U.N. Conference on Disarmament on Tuesday.