(CNN) -- The United States and South Korea on Wednesday plan to end their joint military exercises aimed at warning North Korea to stop acts of aggression.
The military exercises, dubbed Invincible Spirit, are in waters off South Korea. They include 8,000 personnel, 20 ships and submarines, and about 200 aircraft, officials said.
U.S. Defense Department officials said the exercises are in response to the March sinking of the South Korean warship, Cheonan, which killed 46 South Korean sailors.
South Korea has said that an investigation concluded that a North Korean submarine fired a torpedo that sunk the South Korea warship, an assertion the North has denied.
The exercises are intended to send a strong message to Pyongyang to stop "provocative and warlike acts," the U.S. Defense Department said.
The exercises will include anti-sub infiltration exercises, said Cmdr. Jeff Davis of the U.S. 7th Fleet.
"The anti-sub-infiltration exercise works like this: if a sub is coming in to attack a ship, the military finds it and prosecutes it," he said.
Davis said there was a "renewed desire" and urgency to focus on the exercise after the Cheonan sinking. North Korea has criticized the exercises.
"The U.S. provocations amount to trespassing on the off-limits fixed by the DPRK and it, therefore, feels no need to remain bounded to the off-limits drawn by the U.S.," the state-run Korean Central News Agency quoted a North Korean foreign ministry spokesman as saying.
It continued, "It is the mode of the DPRK's counteraction to react to sword brandishing in kind. The DPRK is prepared for both dialogue and war. It will remain unfazed by military threat and sanctions."
Earlier, North Korea had heightened its threats against the military exercises.
North Korea "will legitimately counter with [its] powerful nuclear deterrence the largest-ever nuclear war exercises to be staged by the U.S. and the South Korean puppet forces," KCNA reported.
Democratic Sen. Carl Levin of Michigan downplayed the threats from North Korea.
"I think North Korea is just too interested in their own survival to do anything that could end that regime," Levin said Sunday on C-SPAN's "Newsmakers" program.