Seoul, Aug 9 : South Korea and the US plan to kick off preliminary military drills next week ahead of their major combined exercise later this month, informed sources said on Tuesday. The allies are set to begin the four-day South Korea-led crisis management drills on Tuesday in the run-up to the Ulchi Freedom Shied (UFS) exercise set to run from August 22-September 1, Yonhap News Agency quoted the sources as saying. Led by South Korea's Joint Chiefs of Staff, the drills are designed to practice a set of procedures to respond to possible pre-war crisis scenarios. They are a computer simulation training based on the allies' wartime contingency plans. The UFS involves two parts -- the first on repelling attacks and defending the greater Seoul area, and the other on counterattack operations. The upcoming exercise comes as the allies are striving to strengthen combined defence through measures, including expanding and publicising training programs, amid concerns the North could escalate tensions by conducting a nuclear test or other provocative acts. /IANS