The allies plan to continue the Maritime Counter Special Operations Exercise (MCSOFEX) through Friday in the East Sea and the Yellow Sea, also known as the West Sea.
It involves the U.S. 7th Fleet's aircraft carrier USS Ronald Reagan (CVN-76) and two Arleigh Burke-class destroyers -- the USS Stethem (DDG-63) and the USS Mustin (DDG-89).
The carrier strike group will train with South Korean warships and other defense assets, such as the Sejong the Great Aegis ship and P-3 Orion anti-submarine aircraft in the East Sea.
A unit of U.S. special forces tasked with carrying out "decapitation" operations is aboard a nuclear-powered submarine in the group, according to a defense source.
Among other assets mobilized are F-15K, FA-18 and A-10 fighter jets, as well as AH-64E Apache attack helicopters, Lynx and AW-159 Wild Cat naval choppers.
The U.S. has also deployed a Joint Surveillance Target Attack Radar System (JSTARS) plane to closely monitor the North's ground and naval forces.
The joint training is aimed at promoting "communications, interoperability and partnership in the (U.S.) 7th Fleet area of operations," the fleet said.
It initially announced that the practice around the peninsula will end next Thursday but later corrected the date to Friday.
Meanwhile, the U.S. has sent a B-1B Lancer strategic bomber, F-22 Raptor stealth fighter jets and several other types of high-profile defense assets to the Seoul air show to open this week.
"Approximately 200 U.S. personnel are expected to participate in the Seoul International Aerospace and Defense Exhibition (ADEX) 2017, scheduled from Oct. 17-22 at the Seoul K-16 airport," the 7th Air Force said.
Among the U.S. military aircraft to join the biennial event are the F-22 Raptor, B-1B Lancer, A-10 Thunderbolt II, C-17 Globemaster III, C-130J Hercules, KC-135 Stratotanker, E-3 Sentry, U-2 Dragon Lady and RQ-4 Global Hawk, it added.
Also fielded will be the Air Force's fifth-generation fighter, the F-35A Lightning II, U.S. Navy P-8A Poseidon and a U.S. Army CH-47F Chinook.
"This year's air show will feature demonstrations from U.S. Air Force F-22 Raptors assigned to the 3rd Wing, Joint Base Elmendorf-Richardson, Alaska," the 7th Air Force said.
More than 400 defense firms from 33 countries plan to participate in the ADEX to begin Tuesday. By YONHAP.