North Korea.Pyongyang had offered a moratorium on nuclear testing if this year's joint drills were cancelled -- a proposal rejected by Washington as an "implicit threat" to carry out a fourth nuclear test.
The Key Resolve and Foal Eagle exercises are a perennial source of volatile tensions on the divided Korean peninsula.
Seoul and Washington insist they are defensive in nature, but they are regularly condemned by Pyongyang as provocative rehearsals for invasion.
"Key Resolve" lasts just over a week and is a largely computer-simulated exercise, while the eight-week "Foal Eagle" drill involves air, ground and naval field training, with around 200,000 Korean and 3,700 U.S. troops.
Both exercises will begin on March 2, with Key Resolve lasting until March 13 and Foal Eagle winding up on April 24, a South Korean Defence Ministry front man said.
North Korea has regularly resorted to missile tests and high-decibel bellicose rhetoric in expressing its displeasure with the exercises in the past.
In 2013, the drills fueled an unusually sharp and protracted surge in military tensions, with Pyongyang threatening a pre-emptive nuclear strike, and nuclear capable U.S. stealth bombers making dummy runs over the Korean peninsula.
In a speech to the ruling party's Central Military Commission at the weekend, North Korean leader Kim Jong-Un directed the army to ensure its combat readiness in order to react to "any form of war ignited by the enemy."
There are close to 30,000 U.S. troops permanently stationed in South Korea and, under current arrangements, the U.S. would take operational command of the allies' combined forces in the event of a conflict with the North.
"Exercising our multi-national force is an important component of readiness and is fundamental to sustaining and strengthening the alliance," General Curtis Scaparrotti, commander of the allies' Combined Forces Command, said in a statement.
"The United Nations
...an idea whose time has gone...
Command has informed the Korean People's Army in North Korea ... about Foal Eagle exercise dates and the non-provocative nature of this training," the statement said.
There was no immediate response from Pyongyang to the formal announcement of the drill dates, but South Korean Defence Ministry front man Kim Min-Seok said nothing would derail the exercises.
"North Korea's position and provocative remarks will have no impact," Kim told a press briefing.