South Korea will become a leading member of a U.S.-led multinational initiative aimed at preventing the proliferation of weapons of mass destruction, a diplomatic source here said Monday, a development that could spark tensions with nuclear-armed North Korea.

Key members of the Proliferation Security Initiative have agreed to accept South Korea as a member of its core Operational Experts Group, a decision which will become official at the upcoming OEG meeting, the unnamed source said.

The 20-member OEG acts as the steering committee of the PSI, which currently has over 90 member states including the U.S., Japan, Canada and Singapore. The newest round of the OEG meeting will be Nov. 1-2 in Tokyo.

Seoul first became a member of the PSI last May, shortly after the North conducted its second atomic test.

By becoming a leading member, Seoul will be able to “better monitor illegal weapons trade and related activities in North Korea,” the source in Seoul said.

South Korea, which is technically still at war with the communist North as their 1950-53 conflict ended in a truce, believes Pyongyang torpedoed the Cheonan warship in March, claiming the lives of 46 sailors. North Korea denies the accusation.

The PSI was launched in 2003, mainly aimed at developing and practicing effective procedures to prevent the spread of weapons of mass destruction. The idea of the PSI was first developed by Washington after 15 scud missiles found on board a North Korean freighter had to be released due to the lack of international rules to have them confiscated.

The PSI participants share an agreement that allow the interdiction of third-country ships carrying nuclear materials on the high seas.

North Korea, which conducted nuclear tests in 2006 and 2009, and left the multinational talks aimed at its denuclearization, is one of the main targets of the PSI and is also among the countries opposed to the international drive.

Critics of the PSI, such as China, Iran and North Korea, claim the declaration to stop ships on the high seas was a violation of the international law that guarantees the freedom of the seas.

Pyongyang also suspects the blockade of ships and planes under the PSI as an instrument of an aggressive war planned by Washington.

By Shin Hae-in (hayney@heraldcorp.com)