South Korea plans to formally notify North Korea and other neighboring countries early next month of its plan to conduct annual military exercises with the United States that Pyongyang has demanded be called off, a government source said Sunday.

The South Korean and U.S. militaries are scheduled to hold the annual Key Resolve command post exercise for two weeks from late February to early March to improve their joint combat readiness and capabilities to deter threats from North Korea.

After the Key Resolve exercise, the two countries plan to hold a field training drill, called Foal Eagle, through the end of April. The exercise will involve a large number of troops from both sides.

"We will notify China, other neighboring countries and North Korea of the schedule and purposes of Key Resolve and Foal Eagle in accordance with international practice," the source said. "After the Lunar New Year holiday, we will offer explanations through military diplomacy channels and the Military Armistice Commission."

The defense ministry plans to call in military attaches at the Chinese, Japanese and Russian embassies in Seoul early next month to explain that the Key Resolve and Foal Eagle exercises are annual defensive drills, the source said.

This year's Key Resolve exercise will be similar in scale to those of previous years and will include maritime maneuvers involving Aegis-equipped destroyers, submarines and guided missile cruisers. But it won't involve U.S. aircraft carriers or strategic bombers, the source said.

North Korea has long denounced Key Resolve and Foal Eagle maneuvers as a rehearsal for an invasion of the communist nation, though the South and the U.S. have repeatedly said that the drills are defensive in nature.

Earlier this month, the North demanded the cancellation of the upcoming joint exercises while proposing that the two Koreas stop military provocations and mutual slandering to improve bilateral relations.

South Korea has rejected the demand, saying it will hold the exercises as planned.

Last year, North Korea sharply escalated tensions on the divided peninsula as it churned out near-daily war threats against the South and the U.S. in anger over the annual drills.

About 28,500 U.S. troops are stationed in South Korea to help defend the ally from North Korea, a legacy of the 1950-53 Korean War that ended in an armistice rather than a peace treaty. (Yonhap News)