South Korea and the US have inked a joint contingency plan in the event of an attack from the North. The new plan comes as regional tensions remain high after Pyongyang’s third nuclear test and outlines joint efforts in case of further "provocative" acts.

Under a new agreement that the two allies called ‘South Korean-led, US-supported’, South Korea will have an option to call on American military assistance in dealing with what South Korean military officials called ‘local’ provocations.

Under ‘provocation’ the new pact means maritime border incursions, shelling of border islands, and infiltration by low-flying fighter jets or Special Forces, AFP reports.

The plan signed by Gen. James D. Thurman, the top American commander in South Korea, and Gen. Jung Seung-jo, chairman of the Joint Chiefs of Staff of the South Korean military, comes concurrently with a longstanding defense treaty between the two countries.

While under the Mutual Defense Treaty signed in 1953 the US was obliged to engage in the event of a full-scale conflict, with the new treaty the US may come to the aid in the response to low-level action such as a limited cross-border incursion.

“By completing this plan, we improved our combined readiness posture to allow us to immediately and decisively respond to any North Korean provocation,” the two allies said in a joint statement after the treaty was signed Friday.

Both Seoul and Washington have been reluctant to give further details on, for example, how far the US would go in its supporting role or when troops are to be sent to directly join South Korea’s contractions against a North Korean ‘provocation’.

Currently there are 28,500 US troops stationed in South Korea.

"It will have the effect of preventing the North from daring to provoke us," South Korean Defense Ministry spokesman Kim Min-seok said Monday.

The two allies said they had been working to improve their contingency plans since 2010 when North Korean artillery attack on island killed four South Koreans. The same year a South Korean warship also sank, killing 46 sailors. Seoul pointed the finger at the North, saying the cause was a North Korean torpedo, but Pyongyang denied the accusations.

Washington-Seoul’s defense plan comes amid escalated tensions on the Peninsula as North Korea has threatened to attack the allies over their military drills and recent UN sanctions that followed Pyongyang's latest nuclear test in February.

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