South Korea and the United States will launch a massive landing drill next week, the climax of an ongoing joint military exercise which North Korea views as an invasion rehearsal.
The amphibious drill will start March 28 and run until April 1 at the port of Pohang, some 360 kilometers (223 miles) south of Seoul, the US-South Korea Combined Forces Command said in a statement.
It will include some 1,000 US Marines, three US amphibious ships and 3,000 South Koreans, Yonhap news agency said.
US sailors and marines from the Bonhomme Richard Amphibious Ready Group and the 31st Marine Expeditionary Unit (MEU) based in Okinawa, Japan, are also participating in the drill, known as Ssangyong in South Korea and the Korean Marine Exchange Program (KMEP) in the United States.
"KMEP is designed to strengthen our interoperability in amphibious operations between the US and ROK (South Korea) Forces, which contributes to the security and stability on the Korean Peninsula as well as the entire Asia-Pacific region", the statement said.
The scale of the drill has been downgraded compared with last year, though it marks the peak of the eight-week Foal Eagle joint US-South Korea military exercise which started on March 2 and is scheduled to end on April 24.
Also beginning early March was the Key Resolve exercise, a computer-simulated command post drill that rehearsed various conflict scenarios and involved around 10,000 South Korean and 8,600 US troops.
Last year as the South and the United States were staging the Ssangyong landing drill, South and North Korea exchanged fire near their disputed sea border.
Annual drills always trigger a surge in military tensions between the two Koreas, which remain technically at war because the 1950-53 Korean conflict ended with a ceasefire rather than a peace treaty.
The United States and South Korea insist their joint military exercises are defensive in nature, but North Korea claims that they, especially the landing drill, are designed to rehearse invasion.
North Korea signalled its displeasure when this year's Key Resolve and Foal Eagle drills began by firing two short-range ballistic missiles into the sea off its east coast.
There were some concerns that Pyongyang might consider conducting a fourth nuclear test, but analysis of recent satellite images of the North's main tests site shows no signs of preparations for an imminent detonation.