The exercise took place as a USA guided-missile submarine arrived in South Korea and envoys from the United States, Japan and South Korea met in Tokyo to discuss the growing threat posed by North Korea's nuclear weapons and missiles program.
It's also moving military assets to the region - including the USS Carl Vinson Navy strike group, though there was some confusion about the timetable, and one of its most powerful submarines - in what analysts say is a show of force.
North Korea often marks significant dates by displaying its military capability and has conducted five nuclear tests.
But with increasingly provocative statements and actions coming from North Korea, the emphasis is on military deterrence.
While US Naval Forces Korea called the visit "routine", a US defence official told CNN it was a show of force to North Korea.
An overview of a national meeting at the People's Palace of Culture in Pyongyang on April 24, 2017 in celebration of the 85th founding anniversary of the Korean People's Army (KPA).
The trio also agreed that China and Russian Federation should play a bigger role in reining in the North, said Kim Hong-Kyun, South Korea's chief envoy on the issue.
"The situation prevailing on the Korean peninsula is so tense that a nuclear war may break out due to the frantic war drills of the US imperialists and their vassal forces for aggression", Gen. Pak Yong Sik said at a "national meeting" of thousands of senior military and civilian officials.
"There is no limit to the strike power of the People's Army armed with our style of cutting-edge military equipment, including various precision and miniaturised nuclear weapons and submarine-launched ballistic missiles", the official Rodong Sinmun newspaper said in a front-page editorial.
The U.S. Navy destroyer, the USS Wayne E. Meyer, began maritime exercises with a South Korean destroyer in the Yellow Sea, west of the Korean Peninsula, Tuesday.
The streets of Pyongyang were quiet.
"So it is a sign that if the North is provoked or there is preemptive action, then a lot of Seoul and its suburbs would be within artillery range of the North". The government also states it will be impossible to determine what type of missile the rogue state has launched until it has struck, with the threat of nuclear or chemical warheads not ruled out.
North Korea's refusal to end its nuclear weapons program has caused massive concern. "Sarin gas doesn't have to be dropped", he said.
Relations between North Korea and the US and South Korea have deteriorated in recent months, as the rhetoric and military posturing on both sides has increased.
Amid the military manoeuvrings, the White House has taken the unusual step of calling the entire US Senate in for a briefing on North Korea Wednesday afternoon.
"This is a real threat to the world", Trump said during his meeting with UN Security Council ambassadors at the White House, referring to North Korea's nuclear and ballistic missile programs.
The countries want to include the clause in a United Nations Security Council resolution draft, among other measures such as prohibiting North Korea from exporting its labour. North Korea reportedly earned US$75 million from the transaction with China.
"At a time when the global community needs to come together to protect the rights of people in the DPRK [North Korea], we are instead witnessing a rise in incitement to armed confrontation", he said.
The carrier group was sent to the region as a warning to North Korea and a show of solidarity with USA allies.
A US aircraft carrier strike group is heading for Korean waters, and leading nuclear envoys from South Korea, Japan, and the United States are meeting in Tokyo.