The three carriers will be likely together in the drills around Monday.
The exercise is taking place while U.S. President Donald Trump is on an Asian tour and presenting a united front with regional leaders.
The war exercises off the tense Korean Peninsula aim to strengthen the alliance's policy of "extended deterrence" against Pyongyang's nuclear and missile threats, South Korea's Joint Chiefs of Staff said in a statement.
The drill is an effort to show North Korea the country's military strength and capability to respond as the nuclear threat continues to loom in Pyongyang, reported the news outlet.
In recent months, North Korea has tested intercontinental ballistic missiles that could reach the US mainland with further development and has conducted its most powerful nuclear test.
The defense ministry, however, has ruled out the possibility of trilateral military drills with Japan.
South Korea and the U.S. started large-scale military manoeuvers on Saturday off the Korean peninsula in which three American aircraft carriers are taking part.
The U.S. and South Korea kick-off a landmark operation in the Western Pacific. They will successively enter the exercise area in global waters east of the Korean Peninsula over the weekend, and at one point around Monday will operate together.
"It is a rare opportunity to train with two aircraft carriers together, and even rarer to be able to train with three", U.S. Pacific Fleet Commander Adm. Scott Swift said on Tuesday.
Show of force coincides with US President Trump's visit to AsiaThis weekend, three American aircraft carriers will be carrying out joint exercises in the waters around the Korean Peninsula.
Trump on Tuesday reiterated his goal to achieve what he called "peace through strength", warning the US could use "the full range of our unmatched military capabilities" against Pyongyang.
Trump had also delivered a sharp warning to North Korea in a speech at South Korea's parliament on Wednesday, telling the country: "Do not underestimate us".