North Korea boasted of being a “;proud nuclear power”; and threatened today to harm the United States if attacked as tensions mounted over a possible crackdown on exports of suspected missile parts from the North.

South Korea's YTN news network reported yesterday that a U.S. Navy destroyer tailing a North Korean ship suspected of carrying missiles and related parts was headed toward Myanmar in what could be the first test of new U.N. sanctions against the North because of its recent nuclear test.

The North Korean cargo ship, the Kang Nam, is expected to travel to Myanmar via Singapore, YTN said, citing an unidentified intelligence source in South Korea.

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.

Two U.S. officials said Thursday the U.S. military had begun tracking the ship, which left a North Korean port Wednesday.

One official said it was uncertain what the ship was carrying but that it had been involved in weapons proliferation before. Both spoke on condition of anonymity.

The sanctions—punishment for an underground nuclear test North Korea conducted May 25—firm up an earlier arms embargo against North Korea and authorize ship searches in an attempt to thwart the regime's nuclear and ballistic missile ambitions.

President Barack Obama said yesterday the U.S. is ready to cope with “;any contingencies”; involving North Korea and vowed not to “;reward belligerence and provocation.”;

Obama said the U.S. is prepared for any North Korean provocation, including the regime's reported threat to test-launch a long-range missile toward Hawaii.

Japanese media have reported the North Koreans appear to be preparing for a long-range test planned sometime around July 4, the Independence Day holiday.

Defense Secretary Robert Gates has ordered additional protections for Hawaii as a precaution.