North Korea says United Nations sanctions imposed because of its nuclear weapons test are an act of war. Pyongyang's first public reaction to sanctions came as a senior U.S. envoy arrived in Seoul as part of high-level diplomacy on the North's nuclear weapons program. Regional governments are concerned there may be another nuclear test soon.

A North Korean television announcer reads a statement from Pyongyang's Foreign Ministry saying the United Nations sanctions against it "cannot be construed otherwise than as an act of war."

The statement also says North Korea "wants peace but is not afraid of war," and "wants dialogue but is always ready for confrontation."

After North Korea exploded a nuclear device last week, the U.N. Security Council passed a resolution that among other things bans the import or export of luxury goods and most military hardware by North Korea. It authorizes member states to search North Korean ships, but rules out the use of force against the North.

U.S. Assistant Secretary of State Christopher Hill, who arrived in Seoul Tuesday, stressed the importance of implementing the resolution fully.

"To make sure we have done all we can to impede North Korea's import or export of nuclear materials - to really make it clear that North Korea will pay a very, very high price for this sort of reckless behavior," he said.

Hill is in Asia this week as part of U.S. efforts to coordinate implementation of the resolution and to discuss ways to bring North Korea back to talks on ending its nuclear programs.

Secretary of State Condoleezza Rice also is due in Seoul Thursday, after visiting Tokyo, for consultations on the North Korea issue. She will visit Beijing on Friday.

A senior South Korean official told journalists in a briefing Tuesday that Seoul is still studying the resolution to determine his country's specific role in implementing it. He adds the South's unique and delicate relationship to the North must be considered.

China's foreign ministry on Tuesday said it would fully comply with the resolution, and warned North Korea not to do anything to aggravate tensions in the region.

The United States government has confirmed that North Korea exploded a nuclear device last week.

The South Korean official said his government is aware of signs the North may be preparing for a second nuclear test explosion. He refused to provide details, but international media have reported there are photographs showing what unnamed intelligence officials describe as suspicious vehicle movements at a nuclear test facility in North Korea.