North Korea called the ongoing South Korean-U.S. military drills a plot to invade the country, as it threatened Tuesday to take unspecified “responsible” military steps in response.

The North’s warning came a day after the South Korean and U.S. forces kicked off their annual computer-simulated command post training and a variety of field exercises for an 11-day run. This year’s drills were to involve 48 field exercises, twice the number conducted last year.

In a statement carried by state media, the North’s Defense Ministry said it “strongly denounces the reckless military drills of the U.S. and (South Korea) for getting more undisguised in their military threat to a sovereign state and attempt for invading it.”

An unidentified ministry spokesperson said North Korea’s military will “continue to watch the adventurist acts of the enemies and conduct responsible military activities to strongly control the unstable security environment on the Korean Peninsula.”

The spokesperson didn’t say what measures North Korea would take, but observers say North Korea will likely carry out missile tests or other steps to bolster its war capability.

South Korea’s Defense Ministry said later Tuesday that its drills with the United States is a regular, defensive training. A ministry statement said South Korea will make an overwhelming response if North Korea launches direct provocations against it during the drills.

North Korea views its rivals’ major military drills as invasion rehearsals, though South Korean and U.S. officials have repeatedly said they have no intentions of attacking the North. North Korea has previously reacted to South Korean-U.S. exercises with launches of a barrage of missiles into the sea.

South Korea’s Joint Chiefs of Staff said last week that this year’s military drills with the United States were designed to neutralize North Korean nuclear threats and would involve live-firing, bombing, air assault and missile interception drills.

Concerns about North Korea’s nuclear program have grown in the past two years, as the North has test-launched missiles at a record pace and openly threatened to use nuclear weapons preemptively. The U.S. and South Korea have expanded their military exercises and increased the deployment of powerful U.S. military assets like aircraft carriers and nuclear-capable bombers in response.

This year, North Korea performed six rounds of missile tests and artillery firing drills. North Korean leader Kim Jong Un also declared his country won’t seek reconciliation with South Korea and vowed to scrap the country’s long-running goal of peaceful unification with South Korea. Kim said North Korea would take a more aggressive military posture along the disputed sea boundary with South Korea.

Experts say North Korea could believe a bigger weapons arsenal would provide it with a greater leverage in future diplomacy with the United States. They say North Korea is desperate to win an international recognition as a nuclear state, a status that it would think helps it win relief of U.S.-led economic sanctions.

North Korea is expected to further dial up tensions with more missile tests and warlike rhetoric this year as the U.S. and South Korea head into major elections. North Korea may stage limited provocation near the tense border with South Korea this year, experts say.

(AP)