The North is threatening to retaliate if those drills get under way eventually. South Korea's Joint Chiefs of Staff said Saturday that marines would go ahead with the drills as scheduled and that the military was ready to respond to any possible provocation.
Meantime, North Korean defectors campaigning for a regime change in Pyongyang have released giant balloons carrying thousands of propaganda leaflets in the air.
The leaflets contain information on the North's shelling of the South Korean island back in November. Four South Koreans were killed in that incident.
The U.S. supports South Korea, saying the country has a right to conduct such a military exercise. However, Russia's Foreign Ministry expressed its "extreme concern" Friday over the drills and urged South Korea to cancel it to prevent a further escalation of tensions.
The Associated Press contributed to this report.