North Korean students take part in a rally held to commemorate the June 25 Anti-U.S. Day in Shinchon, South Hwanghae province, North Korea, June 22, 2009 in this picture released by North Korea's official KCNA news agency on June 23, 2009. REUTERS/KCNA

WASHINGTON (Reuters) - President Barack Obama on Wednesday renewed sanctions against North Korea, declaring that its nuclear program posed a national security risk to the United States and a danger to the Korean Peninsula.

The reclusive communist state has rebuffed U.S. efforts to engage it diplomatically and staged a second nuclear test on May 25 that was internationally condemned and led to the imposition of tougher sanctions the United Nations Security Council.

“The current existence and risk of the proliferation of weapons-usable fissile material on the Korean Peninsula constitute a continuing unusual and extraordinary threat to the national security and foreign policy of the United States,” Obama said in a notice to Congress.

The expanded U.N. sanctions ban all weapons exports from North Korea and most arms imports. U.N. member states are also authorized to inspect North Korean sea, air and land cargo and destroy any goods that violate the sanctions.

Obama has said the U.S. military is prepared for the possibility that North Korea may attempt to launch a missile toward Hawaii in response to the new U.N. sanctions.

His decision to renew separate U.S. restrictions on Pyongyang was expected and followed a White House meeting last week with South Korean President Lee Myung-bak.

Obama promised then to end a cycle of allowing impoverished North Korea to create a nuclear crisis and then granting concessions in the form of food, fuel and other incentives to get Pyongyang to back down.

The North previously has reneged on promises it made in return for such aid.