S. Korea, Japan respond to DPRK's nuclear test

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South Korea says it will join the non-proliferation Security Initiative. The PSI is an effort to intercept shipments suspected of carrying equipment and supplies needed to build weapons of mass destruction.

After Monday's underground nuclear test by the Democratic People's Republic of Korea, South Korea announced Tuesday it would join a US-led initiative to stop the spread of weapons of mass destruction.

Pyongyang has warned it would consider Seoul's full participation in the PSI as a declaration of war.

At a State Ministers Financial Affairs Meeting, President Lee Myung-bak called for more to be done to curtail the DPRK's actions.

Lee Myung-bak, South Korean President, said, "By this nuclear test, we are going to not only cooperate with US, but also with the other six-party-talks participating nations like Japan, China and Russia. And we are going to take previously unseen counter measure actions."

A spokesman for the South Korean president says US President Barack Obama welcomes Seoul's participation in the initiative.

But in an effort to cool the rhetoric, South Korea emphasized the decision to join the PSI was not a threat to its neighbour.

Lee Jong-Joo, Spokesperson of S. Korean Unification Ministry, said, "PSI is not a targeted measure towards North Korea. I mentioned that it is not directly related to South-North relationship. We wish that North Korea does not have the wrong understanding about this."

South Korean President Lee Myung-bak talks with his U.S. counterpart Barack Obama on the telephone at the Presidential house in Seoul, South Korea, Tuesday, May 26, 2009. (AP Photo/Yonhap, Jo Bo-hee)