North Korea warned South Korea against joining international sanctions, saying Wednesday that its neighbour would "pay a high price" if it joins the U.S.-led drive to punish the reclusive country for its nuclear test.

The statement from the North's Committee for the Peaceful Reunification of the Fatherland came as South Korea struggles to determine how it should enforce the United Nations sanctions, including whether to help inspect all North Korean cargo ships suspected of transporting materials for unconventional weapons.

"If the South Korean authorities end up joining U.S.-led moves to sanction and stifle [the North], we will regard it as a declaration of confrontation against its own people … and take corresponding measures," the statement said.

U.S. President George W. Bush dismissed North Korea's threats, saying leader Kim Jong-il was probing for weaknesses in the international community.

"The leader of North Korea likes to threaten," Bush told reporters in Washington. "In my judgment, what he's doing is testing the will of the five countries that are working together to convince him there's a better way forward for his people."

The UN Security Council unanimously adopted a sanctions resolution five days after Pyongyang's Oct. 9 nuclear test, and a South Korean task force met this week to determine how the country should address the measures, including what to do about joint economic projects with North Korea.

South Korea's participation in sanctioning Pyongyang is considered important because it is one of the main aid providers to the impoverished Communist country, along with China.

But both countries have been reluctant to impose stern measures against North Korea. China, North Korea's closest ally, voted for the UN resolution but is concerned that excessive measures could worsen the situation. South Korea has expressed similar concerns, although there was no immediate response to Wednesday's statement from North Korea.

"If North-South relations collapse due to reckless and imprudent sanctions against us the South Korean authorities will be fully responsible for it and will have to pay a high price," said the statement, carried by North Korea's official Korean Central News Agency.

The UN resolution gave member countries 30 days from its Oct. 14 adoption to report on implementing the sanctions.