The chief of a state-run diplomatic academy has raised the need for South Korea and the U.S. to explore effective nuclear doctrine, including a preemptive "first use" approach, to cope with the escalating nuclear threats from North Korea.

In a report issued by the Institute of Foreign Affairs and National Security under the Korea National Diplomatic Academy, Chancellor Yun Duk-min said that the allies need to review Cold War-era nuclear doctrine to find one suitable for the defense of the South.

Pointing to Pyongyang's unceasing push to develop miniaturized nuclear warheads and their delivery means, Yun also said the possibility of the North having already deployed short- and mid-range nuclear-tipped ballistic missiles cannot be ruled out.

"In the face of Pyongyang's threats to use nuclear weapons against the South and the U.S., the South and the U.S. need to review once again their best credible nuclear doctrines including the first-use and the flexible response strategy," he wrote in the report.

Under the first-use approach, a nuclear-armed state publicly states its willingness to be the first to use nuclear arms to deal with its adversaries in wartime or crisis situations.

The flexible response strategy is a Cold War-era approach that features the use of a flexible and balanced range of conventional and nuclear responses to military threats from enemy forces.

In recent weeks, Pyongyang has ratcheted up its military threats against the allies in an apparent response to the ongoing allied military drills and the recent adoption of U.N. Security Council sanctions on it for its nuclear test in January and long-range rocket launch in February.

The communist regime has claimed to have secured the capability to mount a miniaturized nuclear warhead on a ballistic missile and the technology to allow the missile warhead to withstand the massive heat during a rocket's atmospheric reentry. Seoul officials, however, doubt the claim. (Yonhap)