North Korea has threatened war if any of its Navy vessels are searched. A Navy ship, center, patrols the Yellow Sea.

By MARTIN FACKLER and CHOE SANG-HUN


SEOUL, South Korea - After years of incendiary threats and weapons tests, the world has become accustomed to provocations from North Korea. More unusual this time is that South Korea is pushing back.

After North Korea’s recent nuclear test, South Korea swiftly moved to join an American-led effort to search ships for unconventional weapons, despite threats of war from the North if its ships were boarded. South Korea has also lobbied China and Russia to take a unified stance against the North, and supported calls at the United Nations Security Council for new sanctions.

The assertive moves by South Korea’s right-leaning and generally pro-American president, Lee Myungbak, are a sharp departure from the conciliatory stance that the South took in previous standoffs, particularly after the North’s first nuclear test three years ago, when it continued economic aid and investment. South Korea’s reluctance to challenge threats from its neighbor, along with China’s more accommodating policies, made it difficult in the past to enact or enforce tough sanctions on North Korea. Now, the South’s decision to stop acting as the North’s leading protector may open a wider range of options in responding to the nuclear and missile tests, analysts say.

“South Korean aid gave North Korea leverage against the United States,’’ said Choi Jin-wook, a North Korea specialist at the Korea Institute for National Unification, a state-run research organization. “Lee Myungbak has emptied their pockets and weakened their bargaining position.’’

It remains to be seen how much that will translate into punitive actions against the North at the United Nations, where the five permanent Security Council members - Russia, China, the United States, Britain and France - have been joined by Japan and South Korea in trying to work out a new resolution that includes sanctions. There is broad agreement on the need to send a tough message to North Korea, senior diplomats have said, but less consensus on what that should be.

“It is not a normal country, so we have to act cautiously,’’ said Zhang Yesui, the Chinese ambassador to the United Nations. “It is a very closed place, so they act abnormally.
’’It is not even clear that China has the influence to sway the North Korean government, he added.

It is also unclear how far South Korea is willing to push the North. Most South Koreans still abhor tensions with the North and are fundamentally in favor of reconciliation, said North Korea experts.

“If North Korea actually tests South Korea’s resolve, it will put South Korea in a very tough spot,’’ said Kim Il-young, a North Korea specialist at Seoul’s Sungkyunkwan University.

Indeed, South Korean officials have been careful to cast their new approach not as a drastic departure but as more a shift in tone. They say the South remains willing to offer economic aid to the North, but only if it responds with good-faith efforts to curtail its weapons programs.

They also say that they are not trying to provoke the North, which has seemed particularly volatile since its leader, Kim Jong-il, appears to have had a stroke in August.

“This is not at all a hawkish or hard line,’’ said Kim Tae-hyo, the secretary to Mr.Lee for national security. “We still seek contacts with the North. Where we differ is that we demand mutual respect and reciprocity.’’