The annual military exercises are likely to contribute to escalating tensions on the Korean Peninsula, with Pyongyang accusing Washington and Seoul of rehearsing an invasion into the country.
"As for the Key Resolve and Foal Eagle exercises, the total number of the US service members will be slightly larger than the previous year," the defense ministry spokesman said as quoted by Yonhap news agency. However, the spokesman did not specify the exact number of troops to be involved.
In 2014, the Unites States sent 5,200 troops for a two-week Key Resolve drills with South Korea, and about 7,500 US forces were part of Foal Eagle exercise. For South Korea, this figure reached 10,000 troops for Key Resolve and 200,000 for Foal Eagle.
Although North Korea accuses the US and South Korea of rehearsing an aggression, Washington and Seoul claim the nature of the exercises is purely defensive.
North Korea has already carried out two test-fires of missiles in 2015. Last week, the country successfully launched five anti-ship rockets into the Sea of Japan, which is seen as a show of strength ahead of the US-South Korean joint drills.