South Korea plans to spend about US$280 billion over the next 15 years to bolster its military capacity.
The plan is part of a Defense Ministry blueprint to streamline and modernize the military.
The blueprint, called "Defense Reform 2020," centers on cutting the 680,000-strong military to 500,000 in phases through 2020, and introducing high-tech weaponry.
The ministry formally unveiled the reform measures Tuesday, saying the nation's defense budget needs to rise by an average of 11 percent a year until 2015, with a reduced rate thereafter, to fund the changes.
It did not give an estimate for the total cost of the troop cuts and military modernization.
However, on Monday the ministry reported the measures before the parliamentary defense committee, saying it estimates about US$282 billion will be needed to increase the country's military capability.
The ministry said on its Web site that it has to prepare for a changing security situation in northeast Asia and the world.
The ministry also underlined it has to prepare for "transnational and nonmilitary threats," an apparent reference to terrorism, the AP reports.