North Korea has long warned it would consider Seoul’s participation in the Proliferation Security Initiative as a declaration of war against the North.

South Korea was hosting a seminar Wednesday among 15 participating nations in the southeastern city of Busan, to be followed Thursday with naval interdiction drills involving South Korea, the U.S., Australia and Japan in international waters between South Korea and Japan, the Defense Ministry said.

The program, which began in 2003, has been joined by more than 90 countries to help deter trade in weapons of mass destruction and missiles by states including North Korea and Iran. Seoul said last year it was joining the maritime web after the North conducted its second atomic test.

The drills also come amid lingering tension on the divided Korean peninsula following the March deadly sinking of a South Korean warship blamed on Pyongyang.

In May, a multinational investigation led by Seoul concluded that a torpedo fired from a North Korean submarine sank the 1,200-ton warship. North Korea has denied involvement in the sinking that killed 46 South Korean sailors.

The sinking has dimmed the prospects for resuming the stalled international talks aimed at dismantling North Korea’s nuclear programs. North Korea quit the talks last year, but it has expressed willingness to rejoin the talks, which include the U.S., South Korea, China, Japan and Russia.

Seoul and Washington have said the North must first take specific moves to demonstrate its sincerity.

In Beijing, Chinese nuclear envoy Wu Dawei told reporters Tuesday after his meeting with North Korea’s First Vice Foreign Minister Kim Kye Gwan that Pyongyang appeared to have positive stance in resuming the nuclear talks, South Korea’s Yonhap news agency reported Wednesday.

Kim, who served as the North’s top nuclear envoy, was promoted last month from vice foreign minister.

The trip comes two weeks after North Korean leader Kim Jong Il promoted his youngest son, Kim Jong Un, to four-star general and gave him key political posts aimed at an eventual succession in what would became the country’s second hereditary power transition.

The elder Kim took over the authoritarian country in 1994 after the death of his father, national founder Kim Il Sung.

Kim Jong Un made his public debut on Sunday during a massive military parade celebrating the 65th anniversary of the ruling Workers’ Party.