U.S. Army infantry soldiers will arrive in South Korea this week to begin their nine-month mission as part of the rotational force to improve joint readiness against North Korea, U.S. Forces Korea said Monday.

About 800 American soldiers from the 1st Battalion, 12th Cavalry Regiment in Texas are set to arrive at Osan Air Base, south of Seoul, on Wednesday, the 2nd Infantry Division said.

"The addition of a Combined Arms Battalion makes the 2nd Infantry Division a more agile and lethal force, more capable of deterring aggression and defending the Republic of Korea, if called upon," the division said in a release.

Integrating rotational units within the U.S. Army division is "strictly defensive" and designed to increase "readiness and strengthen capabilities" of the allies' forces, it said.

The additional deployment is part of Washington's military rebalancing to the Asia-Pacific region amid rising tensions in the strategically important region, after its troops withdrew from Afghanistan and Iraq after years of war.

It also comes at a time when North Korea is pressuring Seoul and Washington to halt their planned annual drills slated to begin in late February, offering dialogue and reunions of families separated by the 1950-53 Korean War.

Following the execution of young leader Kim Jong-un's once-powerful uncle, Jang Song-thaek, in December, South Korean and U.S. forces have been beefing up their vigilance against potential political instability in the isolated communist state.

Last week, Adm. Samuel Locklear, head of the U.S. Pacific Command, said the Pentagon's increased deployment of rotational troops and advanced weapons to Korea is aimed at maximizing the combat readiness of the allies, saying the allies will go ahead with the planned joint drills.

About 28,500 American service members are stationed in South Korea to help deter aggression from North Korea. (Yonhap News)