Defence Secretary Donald Rumsfeld will authorise a phased pull-back of some 15,000 troops stationed near the demilitarised zone.
Following annual security talks on Monday, Rumsfeld’s opposite number Cho Young-kil acknowledged the plans that will reduce 2nd US Infantry Division front-line strength.
Just under 40,000 American soldiers are stationed in a 56km wide region that separates Seoul and its northern neighbour.
No effect on security
But Rumsfeld insisted any pullback would not weaken the US stance against Pyongyang.
Speaking to journalists at Camp Casey, a spokeswoman for the division, Major Tamara Parker, also assured local media that their motto was still to “fight tonight – we take that seriously”.
Nevertheless, tensions on the Korean peninsula will remain high owing to the sheer volume of lethal weapons and troop numbers in such a confined space.
Both defence secretaries point to Pyongyang's 1.1 million strong army as a "global" threat to peace.
US Korean presence
However, just 11km south of the demilitarised zone that divides the two Koreas, US military camps house thousands of troops in an invasion corridor used by tanks and soldiers during the Korean War in 1950.
Many ordinary Koreans unhappy
with US presence in the capital
The volume of US equipment is similarly large, Rumsfeld was shown MlAl Abrams tanks, Bradley fighting vehicles, AH64 Apache Longbow helicopters, Kiowa warrior scout helicopters and the latest PAC-3 Patriot missile air defence system.
Rumsfeld is scheduled to visit another forward-positioned US military post, Camp Humphreys, before heading south of Seoul to Osan Air Base, where he is to meet service personnel before returning to the United States.
The move is part of a sweeping reorganisation of US troops across the region, including the 47,000 troops based in Japan.
Analysts say the consolidation of forces could lead to reductions in the 37,000 US troops in South Korea, although officials denied that was on the agenda.
However, the two sides failed to reach agreement on a US-backed move to relocate troops from Seoul, designed to ease protests over their military presence.
Scores of anti-US demonstrators staged protest rallies near the venue for the talks that also dealt with Iraq. Hundreds of riot police were on the streets in a show of force.
South Korean activists oppose President Roh Moo-Hyun's decision last week to dispatch some 3000 troops to Iraq in support of US-led occupation forces.
Roh's plan fell short of Washington's reported demand for more than 5000 combat troops.