B-52s participating in the ongoing South Korea-U.S. joint military drills are meant to demonstrate a strong alliance capability in the face of North Korean threats, the Pentagon said Monday.

"This mission highlights the extended deterrence and conventional capabilities of the B-52 Stratofortress while participating in exercises such as Foal Eagle," Pentagon spokesman George Little told reporters.

Foal Eagle, an annual joint exercise, began on March 1 for a two-month run. South Korea and the U.S. are staging another joint military drill, Key Resolve.

On his trip to Seoul, Deputy Secretary of Defense Ashton Carter stated that strategic bombers are joining the exercise. It is unusual for a senior U.S. official to make public specific equipment taking part in such military training.

On March 8, Little said, a B-52 bomber from Andersen Air Force Base in Guam conducted a training flight over South Korea.

"This flight demonstrated one of the many alliance capabilities available for the defense of the Republic of Korea," he added, using South Korea's formal name.

The B-52, used by the Air Force since the 1950s, is a long-range heavy bomber that can carry nuclear or precision-guided conventional ordnance.

The B-52s participating in the exercises in Korea are part of the U.S. Pacific Command's Continuous Bomber Presence in the Pacific.

"These CBP missions are routine and reiterate the U.S. commitment to the security of our allies and partners," said Little.

Despite challenges with fiscal constraints, training opportunities remain important to ensure the U.S. and South Korean forces are battle-ready and trained to employ airpower to deter aggression and defeat any attack against the alliance, Little said.

The U.S. military is confronted with massive spending cuts in efforts to reduce federal budget deficits. The stark reality puts Pentagon officials in a desperate search for priorities and cost-effective operations.

As part of the move, Secretary of Defense Chuck Hagel directed senior staff to conduct a review of strategic choices, force posture, investments and institutional management, according to Little.

"This Strategic Choices and Management Review will define the major decisions that must be made in the decade ahead to preserve and adapt our defense strategy, our force, and our institutions under a range of future budgetary scenarios," he said.

In Seoul, Carter met with several top South Korean officials, including Foreign Minister Yun Byung-se and senior presidential security adviser Kim Jang-soo, Little said. They discussed North Korea's weapons of mass destruction programs, U.S. military presence on the peninsula and alliance commitments, he said.

But he erroneously said Carter met with Kim Byung-kwan, the nominee to be defense minister. Kim has not been confirmed by the National Assembly amid controversy over his qualifications.

Carter met with Defense Minister Kim Kwan-jin. (Yonhap News)