The US has agreed to phase the withdrawal of troops from South Korea after Seoul warned a sudden departure could leave it vulnerable to the North.
The sudden withdrawal would have alarmed Seoul
Washington had originally planned to pull out a third of its troops by the end of 2005, as part of a global realignment plan.
But it will now stretch that withdrawal over three years until 2008.
The Pentagon insists that longer range weapons and better technology will compensate for the troop reduction.
The plan, announced after weeks of negotiations, is that 5,000 US troops will leave South Korea this year, 3,000 next year, 2,000 in 2006, and 2,500 in 2007 and 2008.
That will leave a total of about 24,500 troops in the country.
A Pentagon statement released on Wednesday said the consultations "considered the Korean public's perceptions regarding a potential security gap".
The troop withdrawal is part of a global realignment of US military forces.
The US and South Korea also agreed earlier this year to relocate all of the US troops based in the South Korean capital, Seoul, to a new base further south.
The US has said it will move the 8,000 troops to Pyongtaek, 80km (50 miles) to the south, by December 2008, freeing up money from its prime real estate location.
Both sides have also agreed to eventually relocate 14,000 troops currently based between Seoul and the North Korean border.
Their forward position puts them in range of North Korean artillery, and US officials have said that pulling troops back south of the capital would strengthen the military's hand.
US troops have been stationed in South Korea since the 1950-53 Korean War.