SEOUL — The United States has agreed to a “phased” withdrawal of 12,500 troops in South Korea over the next three years, delaying its original proposal to complete the reduction by the end of 2005, officials from both countries said Wednesday.

The new plan, announced at an afternoon Ministry of National Defense news conference and confirmed moments later by a Pentagon statement, calls for a three-stage drawdown from now to 2008.

The agreement marks the first concrete steps in what the Pentagon says will be a worldwide reshuffling of U.S. troops to better reflect post-Cold War conditions. In mid-August, President Bush pledged to move 70,000 U.S. servicemembers and 100,000 family members and civilian employees back to the United States over the next decade.

In the first phase, 5,000 U.S. troops would depart South Korea by the end of this year. That number includes the 3,600 soldiers of the 2nd Brigade, 2nd Infantry Division, deployed to Iraq in August. Army officials confirmed last month the 2nd Brigade will head to Fort Carson, Colo., instead of returning to South Korea.

U.S. officials did not specify which units would be included in the 1,400 other troops leaving this year, saying only they are “associated with” the 2nd Brigade.

Another element of the first phase is South Korea’s assumption of several U.S. military missions, including responsibility for the Joint Security Area in the Demilitarized Zone and a rear-area chemical decontamination unit, Pentagon officials said.

In the plan’s second phase, the United States would remove 3,000 troops in 2005 and 2,000 troops in 2006. Again, the affected units were not specified, identified in the Pentagon release only as “combat units, combat support and combat service support units, units associated with mission transfer areas, and other support personnel.”

In the final phase, the United States would redeploy 2,500 troops from “support units” over the 2007-08 time frame, officials said.

U.S. Forces Korea officials referred all questions on the announcement to the Pentagon.

The agreement was reached after several months of negotiations between the two countries and amid associated moves to consolidate and close dozens of U.S. installations in South Korea. The announcement also comes as the United States, South Korea and three other nations are negotiating with North Korea over its nuclear weapons program.

“During these consultations, the United States and South Korea fully considered the combined requirement to maintain a robust deterrent and defense capability while increasing combat capacity,” the Pentagon release read.

“Additionally, consultations considered the Korean public’s perceptions regarding a potential security gap.”

As part of the agreement, the Pentagon also committed to maintaining on the peninsula a multiple launch rocket system battalion and associated counterfire assets, which South Koreans specifically requested.

In recent months, U.S. officials have gone to great lengths to rebut any talk that the reduction would weaken the deterrent value of U.S. forces on the peninsula. The number of “boots on the ground” is less important than the combat capabilities they can bring to bear, officials have said.

U.S. Forces Korea commander Gen. Leon J. LaPorte reiterated that stance late last month in several appearances before South Korean and international media.

“As the combat commander here in Korea, I am very confident in the decisions we’ve made and in the fact that we’ve not created a security vacuum — that capabilities rather than a numerical number is what’s important,” LaPorte said Sept. 9.

Wednesday’s announcement also said U.S. forces would continue a three-year, $11 billion program to enhance the high-tech capabilities on the Korean peninsula and in the region.

“Throughout these consultations, the United States has made clear that it remains committed to the defense of the Republic of Korea, to the security and stability of the region and to a strengthened Republic of Korea-U.S. alliance,” the Pentagon release read.

South Korean officials reacted favorably to Wednesday’s announcement, with political analysts saying it would be viewed as a diplomatic victory for South Korean president Roh Moo-hyun.

“Continuous voices raising possible security concerns persuaded Washington, bolstered by the U.S. intention to maintain good relations with Seoul,” Park Seon-sup, of the Korea Institute for Defense Analysis, told the Chosun Ilbo newspaper.

Roh came under intense public criticism for agreeing to send almost 4,000 South Korean troops to bolster U.S. forces in Iraq. The completion of that deployment has led to heightened terror concerns in South Korea.

The new agreement also gives the South Korean military more time to bolster its own capabilities, officials said. Roh has called for a military fully capable of unaided self-defense over the next 10 years.

Facts and figures ...

U.S. force reduction goals

2004: 5,000 troops, including 3,600 2nd Brigade troops in Iraq

2005: 3,000 troops from unspecified units

2006: 2,000 troops from unspecified units

2007-08: 2,500 troops from unspecified units

(Source: Department of Defense)

Base closures

Camp Bonifas (2004)

Camp Liberty Bell (2004)

Camp Edwards (2004)

Camp Garry Owen (2004)

Camp Giant (2004)

Camp Greaves (2004)

Camp Howze (2004)

Camp Stanton (2004)

Camp Falling Water (2004)

Yongsan Garrison (2008)

(Source: U.S. Forces Korea)