The US and South Korea have completed joint action plans for responding to a regime collapse and other internal emergency situations in North Korea, a report says.

"South Korea and the US had long worked on Concept Plan 5029, to prepare for a regime collapse and other internal emergencies in North Korea," Yonhap News Agency reported Sunday, quoting an informed South Korean official.

The report added that the bilateral discussions started last year after the Lee Myung-bak government pushed to convert the concept plan into a complete and operational plan.

“Since its inauguration last year, the Lee Myung-bak government has pushed to convert the concept plan into an operational plan and it was recently completed," an informed South Korean official was quoted by the agency as saying.

The plan is a case-by-case response to different emergency situations in North Korea, if a civil war breaks out.

"If the South Korea-US combined forces intervene in North Korea's internal instabilities, the South Korean military will assume the leading role in consideration of neighboring countries, while the US military will be responsible for the removal of the North's nuclear facilities and weapons," added the report.

North Korea has strongly protested the plan, saying Washington and Seoul were preparing to invade the state.

Some 28,500 US troops are situated in South Korea to bolster its' 655,000-strong armed forces against North Korea's 1.2 million-member military.

Observers believe that the plan constitutes an out-right conspiracy to destabilize and overthrow a sovereign government, a blatant violation of international law.

RZS/MB