The contingency plan signed in the wake of escalating provocations from the North Korea, gives the U.S. troops expanded role in protecting the South Korean interests, Voice of America reported.
The agreement was signed Friday by South Korea's Joint Chiefs of Staff Chairman General Jung Seun-jo and the commander of U.S. forces in South Korea, General James Thurman.
Seoul's Joint Chiefs of Staff said Monday that the plan is designed to counter a future limited attack by North Korea, but details were not released, the Associated Press reported.
The U.S. already offers protection to the South against a nuclear attack or in case of a full-fledged war between the two Koreas, through a separate plan. However, this does not cover the low-level attacks or an incursion from the North such as the one in which North Korean artillery attacked a South Korean island in 2010 killing four.
Under the new pact, Seoul can seek immediate assistance from the U.S. in the case of minor provocations on the border.
"This allows both nations to jointly respond to the North's local provocations, with the South taking the lead and the U.S. in support," South Korean Defense Ministry Spokesman Kim Min-seok said, BBC reported.
"It will have the effect of preventing the North from daring to provoke us," he added.
The new deal was conceived in 2010 following the North’s attack on a border island and sinking of a South Korean warship allegedly by the North in the same year. However, Pyongyang denies the South’s allegations on sinking the war ship.
The North, which is said to be furious over U.N. sanctions and the U.S.-South Korea joint military drills, has threatened to launch nuclear strikes against the U.S and its allies. What's more, Pyongyang has declared the 1953 armistice that ended the Korean War “invalid" in response to the military drills.
The new pact between the U.S. and the South is expected to draw irked responses from the North, which accuses the allies of planning to attack the North Korea.
There are 28,500 U.S. troops stationed in South Korea.
The United States and South Korea signed a new military pact that would help the allies to launch combined counter provocative measures against North Korean aggression, military officials said.