March 1 (UPI) -- The United States and South Korea started their annual joint military drills Wednesday, two weeks after North Korea conducted a missile test.
Foal Eagle, which involves ground, air and naval forces, is scheduled to run through April, South Korea's defense ministry said.
The two nations also are planning a computer-simulated command post exercise, called Key Resolve, starting March 13.
On Wednesday, North Korea denounced the exercises and alerted its armed forces to prepare for a "merciless" counterstrike against what it said was potential enemy aggression.
About 3,600 U.S. soldiers will participate in Foal Eagle, a U.S. Forces Korea spokesman told Yonhap News Agency.
Taking part in the drills will be the USS Carl Vinson aircraft carrier and two kinds of aircraft -- F-35B supersonic stealth jets and Osprey tiltroter planes that can lift off and land vertically, like helicopters. B-1B and B-52 bombers may also be used in the exercises, the spokesman said.
On Feb. 12, North Korea test-fired a new type of intermediate-range ballistic missile -- the first provocation since the inauguration of U.S. President Donald Trump.
On Wednesday, North Korean leader Kim Jong Un visited an army unit's headquarters, praising the troops for their "vigilance against the U.S. and South Korean enemy forces that are making frantic efforts for invasion," the state-run Korean Central News Agency reported.
South Korean Defense Minister Han Min-koo spoke on the phone with U.S. Defense Secretary James Mattis, "stressing the need to bolster the drills," according to a statement issued by the ministry. Mattis vowed an "effective and overwhelming response" against nuclear weapons by the North.
Protesters participated in a rally outside the U.S. Embassy in Seoul, alleging the drills will "bring the peninsula sharply closer to the brink of a nuclear war."
Also Wednesday, South Korea's Acting President Hwang Kyo-ahn said his country would respond strongly to any provocations by the North and called for tougher U.N. sanctions against Pyongyang.
"The government will strive to make the North realize the uselessness of its nuclear weapons" and the strength of the U.S. missile arsenal, Hwang said in an address marking the anniversary of his country's independence movement against Japanese colonial rule.
Last year, about 290,000 South Korean troops and about 15,000 American forces took part in the drills.