North Korea's (searchmilitary may have aimed a laser at a U.S. helicopter in March, a U.S. official said Tuesday, shortly after the North reaffirmed its decision to nullify an agreement to remain free of nuclear weapons.

The aircraft's sensors detected the unknown type of laser while it was flying near the heavily fortified frontier that divides the two Koreas, the U.S. military official said on condition of anonymity. No one was injured and no equipment was damaged in the incident.

"Two USFK (United States Forces Korea) pilots during a routine training mission in March were alerted by onboard laser detecting equipment that laser systems may have illuminated their aircraft," he said. He did not elaborate on the kind of laser.

The Washington Times said in an article in Tuesday's edition that two U.S. Apache (search) attack helicopters were fired on by a weapon that had the characteristics of a Chinese laser gun.

North Korea initially announced in Korean late Monday that a 1992 agreement with South Korea (search) not to deploy nuclear arms on the Korean Peninsula (searchwas nullified, accusing the United States of derailing the deal. It repeated the declaration Tuesday in English.

"The inter-Korean declaration on denuclearization of the Korean Peninsula was thus reduced to a dead document due to the U.S. vicious hostile policy to stifle the DPRK with nukes," the North's official news agency, KCNA, said. DPRK stands for the Democratic People's Republic of Korea, the North's official name.

The accord was the last remaining legal obligation under which North Korea was banned from developing atomic arms. In January, North Korea withdrew from the Nuclear Nonproliferation Treaty.

A different U.S. military official in Seoul, also speaking on condition of anonymity, said Tuesday that North Korea is believed to have exported $580 million worth of missiles to Iran, Pakistan, Libya, Syria, Egypt, Yemen and the United Arab Emirates in 2001.

In December, a shipment of North Korean missiles bound for Yemen was briefly stopped in the Arabian Sea.

North Korea accuses the United States of planning to attack the communist country. Washington says it wants to use dialogue to resolve the nuclear crisis, although U.S. officials have not ruled out a military option.

North Korea "keenly felt that the denuclearization of the Korean Peninsula would only remain as a daydream unless the U.S. drops its hostile policy toward the DPRK," KCNA said Tuesday.

The comments came as President Bush and South Korean President Roh Moo-hyun were about to meet Wednesday in Washington to discuss North Korea's nuclear programs.

Roh said he will never condone North Korea's nuclear development, and that Seoul and Washington agree the nuclear standoff with the North must be solved peacefully "by all means."

"It is incumbent upon Pyongyang to give up its nuclear project and come forward as a responsible member of the international community," he said. "When the North takes this route, the Republic of Korea and the international community will extend the necessary support and cooperation."

The nuclear crisis flared in October, when Washington said North Korea admitted having a secret nuclear program in violation of a 1994 treaty with Washington.