A US nuclear-powered aircraft carrier is operating in waters off the Korean Peninsula as South Korea and the US kicked off preliminary military exercises Tuesday, military sources confirmed to The Korea Herald.

The USS Abraham Lincoln (CVN-72) “has entered the international waters of the East Sea” as of Tuesday, an informed military official, who wished to remain anonymous due to the sensitivity of the issue, said.

The operation of the USS Abraham Lincoln off the Korean Peninsula in the East Sea comes amid growing concerns that North Korea could conduct a major weapons test on the occasion of the 110th birth anniversary of the late founder Kim Il-sung on April 15. 

Seoul and Washington have braced for the possibility that Pyongyang could resume nuclear explosive testing or launch more intercontinental ballistic missiles in the foreseeable future.

The USS Abraham Lincoln is “operating in the vicinity of Tsushima Island” located between South Korea and Japan and moving northeastward as of Tuesday morning, the military source said. The nuclear-powered aircraft carrier is scheduled to stay in the waters for around five days.

But the source elucidated that it has not yet been decided whether the USS Abraham Lincoln strike group will join the upcoming South Korea-US joint military exercises or conduct naval drills with the South Korean Navy’s vessels.

The South Korean military also “has not been informed about if the USS Abraham Lincoln aircraft carrier plans to move toward the South Korean waters” or shift its direction, the source said. 

But the USS Abraham Lincoln could enter the South Korean waters “if needed” and depending on circumstances on the Korean Peninsula.

The US Navy on Tuesday afternoon confirmed to The Korea Herald that the Abraham Lincoln Carrier Strike Group is “conducting bilateral operations with the Japan Maritime Self-Defense Force in the Sea of Japan,” explaining that the military drills are “occurring within international waters and airspace.”

Lt. Mark Langford, US Navy Spokesperson, said such routine bilateral exercises aim to “reassure our allies and partners of the US commitment to maintaining a free and open Indo-Pacific.”

“Our training enhances the credibility of conventional deterrence by demonstrating the strength of our bilateral partnerships,” the spokesperson said in an email.

But the US Navy did not answer questions about if the USS Abraham Lincoln plans to enter the South Korean waters, reiterating that the purpose of the deployment is to “maintain regional security and stability, keep sea lanes open, and to reassure our allies and partners” in the Indo-Pacific region. 

The dayslong operation of the USS Abraham Lincoln, which can accommodate around 80 aircraft, near the east of the Korean Peninsula, comes after more than a four-year hiatus.

The last time any US nuclear-powered aircraft carrier operated in the waters between Japan and South Korea was in November 2017.

At the time, the USS Ronald Reagan (CVN 76), USS Nimitz (CVN 68) and USS Theodore Roosevelt (CVN 71) strike groups conducted a rare three-carrier strike force exercise with South Korea’s Navy vessels in the region. 

The deployment is noteworthy in light of the US military’s recent move to enhance military readiness posture on the Korean Peninsula following North Korea’s recent spate of missile launches.

The US Indo-Pacific Command in March said it has enhanced intelligence, surveillance, and reconnaissance capabilities and ballistic missile defenses on the Korean Peninsula.

In addition, the USS Abraham Lincoln in mid-March led military drills over the Yellow Sea along with US Air Force aircraft to demonstrate the US’ “resolve and commitment” to defend regional allies against North Korea.

The US Seventh Fleet Public Affairs said the carrier-based air demonstration was conducted in response to North Korea’s consecutive ballistic missile launches and the two tests involving a new intercontinental ballistic missile system.

Adm. Samuel J. Paparo, commander of the US Pacific Fleet, earlier this month also said during a media roundtable that the US Navy is “cultivating some options” to demonstrate its “commitment to the security, the stability and the well-being of the Republic of Korea.”

On Tuesday, South Korea and the US began the four-day crisis management staff training (CMST), preliminary military exercises, another military official with knowledge of the matter confirmed to The Korea Herald on condition of anonymity.

The CMST is led by South Korea’s Joint Chiefs of Staff and aims to examine the allies’ readiness posture to respond to potential contingencies that might occur in the prewar phase and normalize the situation.

Seoul and Washington are scheduled to conduct their computer-simulated Combined Command Post Training (CCPT) from April 18 to 28.

But South Korean Defense Ministry spokesperson Boo Seung-chan on Tuesday declined to confirm the schedules of the CMST and CCPT during a regular press briefing.

Boo said South Korea and the US have agreed to “announce the formation, scale and the schedule of the joint military drills by mutual consent.”

Both sides plan to make an official announcement on the beginning of the joint military drills on Sunday, the source said.