The United States has agreed to withdraw 12,500 troops from South Korea over several years rather than pulling them all out by the end of next year, as was initially planned, the Pentagon and South Korean officials said Wednesday.

The pullout -- unveiled earlier this year as part of the Pentagon's plan to make U.S. troops stationed abroad more mobile for deployment to global hot spots -- marks one of the most significant reductions in U.S. troops on the Korean Peninsula in decades. However, South Korean officials, whose military was scheduled to pick up the slack, complained that the massive withdrawal was being planned too quickly and that they needed more time to take over the missions now run by U.S. forces. They also said a rapid withdrawal could generate a "security gap" with North Korea.

After months of negotiations, U.S. and South Korean officials decided to conduct the first phase of the withdrawal this year, with 5,000 U.S. troops leaving South Korea, including the 2nd Brigade Combat Team and associated units, some of which have already been dispatched to Iraq.

During 2005 and 2006, the United States will redeploy a total of 5,000 troops, according to a Pentagon statement. From 2007 to 2008, the redeployment will be completed with the withdrawal of 2,500 troops, primarily support units and personnel.

Under the agreement, South Korean forces will take over security from U.S. troops at the joint security area in the Demilitarized Zone separating North and South Korea -- the world's most heavily militarized border.

"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 said in the statement. "Additionally, consultations considered the Korean public's perceptions regarding a potential security gap."

-- Anthony Faiola