In this undated photo released earlier this week by Korean Central News Agency, North Korean leader Kim Jong-il, right, inspects the command of the 7th Infantry Division of the Korean People's Army at an undisclosed location in North Korea. (Korean Central News Agency/Korea News Service/Associated Press)

North Korea threatened on Wednesday to "wipe out" the United States in the event of a new war on the Korean Peninsula, as international observers watched for signs the regime would perform new missile tests in the coming days.

The warning came as a U.S. navy destroyer was tracking a North Korean ship suspected of attempting to transport illicit weapons to Burma. The pursuit is seen as the first test of sanctions passed by the UN Security Council as a response to Pyongyang's underground nuclear test in late May.

North Korea has said it would consider an interception to be a declaration of war. On Wednesday, it accused the U.S. of seeking to provoke another Korean War.

"If the U.S. imperialists start another war, the army and people of Korea will … wipe out the aggressors on the globe once and for all," the official Korean Central News Agency said.

The Korean War ended in a truce in 1953, not a peace treaty, leaving the peninsula in state of war.

In recent months, Pyongyang has sparked the fury of the international community by shunning six-party negotiations and resuming its nuclear program in defiance of the UN Security Council.

Meanwhile, reports emerged in South Korea that the North's leader, Kim Jong-il, appointed his son, Kim Jong-un, to head the country's spy agency to prepare him to inherit the leadership.

Seoul's Dong-a Ilbo newspaper reported that Kim ordered senior officials at the State Security Department in March to "uphold" his youngest son as head of the agency, while doling out foreign-made luxury cars to the officials as gifts.

The 67-year-old Kim reportedly suffered a stroke last year and has appeared gaunt in recently released photos, prompting further speculation about his health and the stability of the regime.

With files from The Associated Press