"The exercise is aimed at enhancing deterrence against North Korea's nuclear and missile threats and showing off preparedness to fend off any provocative acts by the North", a ministry spokesman said.
"The future of this region and its attractive people must not be held hostage to a dictator's twisted fantasies of violent conquest and nuclear blackmail", he said during a speech in Vietnam at the annual Asia Pacific Economic Cooperation (APEC) forum.
Tensions over the North's weapons programme have surged in recent months, as Pyongyang carried out a sixth nuclear test ─ by far its largest to date - and test fired dozens of missiles, some capable of reaching the USA mainland.
During his trip to Asia, Trump attempted a symbolic stare-down of Kim this week at the heavily fortified border that separates North and South Korea. But heavy fog forced the cancellation of Trump's plans, and he was forced to turn back.
American leaders, including President Donald Trump, have warned the belligerent regime not to "underestimate" or "test" US strength.
He leaves for the Philippines on Sunday afternoon where he will attend the ASEAN summit of Southeast Asian leaders.
South Korea and the United States on Saturday kicked off a joint naval exercise in the Sea of Japan involving three US aircraft carriers amid heightened tensions on the Korean Peninsula.
The three flattops - USS Ronald Reagan, USS Nimitz and USS Theodore Roosevelt - will sail one by one into the waters east of Korea for the four-day drill.
The three carriers will be likely together in the drills around Monday, according to a South Korean military official, who didn't want to be named, citing office rules.
Also to be mobilized are 11 U.S. Aegis ships and seven South Korean warships.
The Pentagon said on Wednesday the drill involving three aircraft carrier strike groups in the Western Pacific would be carried out for the first time in a decade, confirming a Reuters report.
The goal of the exercise was to demonstrate the U.S. Navy's ability to "operate multiple carrier strike groups as a coordinated strike force efforts", the navy said, adding that the three carrier strike groups will conduct training including "air defense drills, sea surveillance, replenishment at sea, defensive air combat training, close-in coordinated maneuver".
North Korea jolted major world leaders when it carried out the strongest of its six-ever nuclear tests in early September, claiming to have used a hydrogen bomb.
"The U.S., under my administration, is completely rebuilding its military, and they're spending hundreds of billions of dollars to the newest and finest military equipment anywhere in the world, being built right now".