The USS Nimitz, a U.S. Navy aircraft carrier, left port Monday to take part in naval exercises with the South Korean military in the Sea of Japan. The nuclear-powered Nimitz is one of the largest warships in the world, with a displacement of more than 100,000 tons.
South Korea, meanwhile, deployed its King Sejong destroyer, a warship equipped with the Aegis ballistic missile defense system.
North Korea said it viewed the latest series of military drills as part of an aggressive policy by its rivals.
"The latest maneuver is dangerous because it comes right after South Korea and the United States concluded the annual Foal Eagle military drills all across the Korean Peninsula," a statement published by South Korean news agency Yonhap read.
Foal Eagle was a two-month military drill concluded in April by the U.S. and South Korean militaries. The North Korean government said it viewed those drills as preparation for war.
Both the United States and South Korea governments have expressed concern about the security situation on the Korean Peninsula following the February test of a nuclear device by North Korea.
South Korean President Park Geun-hye met last week with U.S. President Barack Obama to discuss the security situation in the region.