(Yonhap) -- The United States plans to redeploy a chemical unit to South Korea to strengthen the combined deterrence against North Korea, nine years after its departure from the Asian ally, an American military official said Saturday.

   The 23rd Chemical Battalion withdrew from South Korea in 2004 as part of an agreement calling for South Korea to take over 10 major defense missions from the United States. Other transferred duties included solely undertaking missions to patrol the heavily armed border.

   The 290-member battalion, which consists of three smaller units, will be relocated from the Joint Base Lewis-McChord to the U.S. Army's Camp Stanley in Euijeongbu, north of Seoul, by March next year, a U.S. Forces Korea official said.

   The move is aimed at bolstering deterrence against threats on the Korean Peninsula, USFK said.

   Last month, the U.S. military also brought in 78 mine resistant ambush protected (MRAP) vehicles, and plans to introduce an additional 300 MRAPs, officials said.

   USFK also plans to bring in precision-guided Excalibur shells capable of striking artillery batteries in North Korea by the end of the year, while additionally deploying Patriot-3 missiles and ATACMS surface-to-surface missiles, sources said.

   The United States keeps 28,500 troops in South Korea to help deter North Korean aggression, a legacy of the Korean War that ended in a truce, not a peace treaty, leaving the divided Korean Peninsula still technically at war.