SEOUL, South Korea — President Barack Obama assured Americans in an interview broadcast today the U.S. is prepared for any move North Korea might make, amid reports Pyongyang is planning a long-range missile test to follow up its provocative nuclear test last month.

Defense Secretary Robert Gates ordered additional protection for Hawaii as a precaution, though experts say North Korea doesn't yet have a ballistic missile that can reach Hawaii and has not mastered mounting a nuclear bomb on a long-range missile.

Still, North Korea declared itself a "proud nuclear power" and warned it will strike if provoked.

"It would be a grave mistake for the U.S. to think it can remain unhurt if it ignites the fuse of war on the Korean peninsula," the country's main Rodong Sinmun said in a commentary.

The U.S., which has 28,500 troops in South Korea, has said it has no such intentions.

Obama assured Americans "this administration — and our military — is fully prepared for any contingencies." His interview with CBS News' "The Early Show" was taped Friday for broadcast today.

"I don't want to speculate on hypotheticals," Obama said. "But I want ... to give assurances to the American people that the t's are crossed and the i's are dotted in terms of what might happen."

A U.S. destroyer, meanwhile, was shadowing a North Korean cargo ship suspected of carrying illicit weapons.

The Kang Nam, accused of engaging in illicit trade in the past, appeared to be heading toward Myanmar, a South Korean intelligence official said Monday. He said the ship is believed to be transporting banned weapons. The official spoke on condition of anonymity, citing the sensitive nature of the information.

Myanmar's military government, which faces an arms embargo from the United States and the European Union, reportedly has bought weapons from the North in the past.

The Kang Nam is the first ship being tracked under new U.N. Security Council sanctions designed to punish the North for its defiant underground nuclear test last month. It could become a test case for the interception of North Korean ships at sea — a move Pyongyang has said it would consider an act of war.

The sanctions require U.N. member states to inspect vessels believed to contain banned goods — with the consent of the nation whose flag the ship is flying. The resolution also orders member states not to provide fuel and other supplies to North Korean ships suspected of carrying banned items.

However, North Korea is unlikely to allow any inspection of its cargo, making an interception impossible, said Hong Hyun-ik, an analyst at the Sejong Institute think tank.

A Japan-based destroyer, the USS John S. McCain, was relatively close to the North Korean ship but had no orders to intercept it, a senior U.S. military official said Friday.