Seoul, South Korea ? South Korean President Roh Moo-hyun, in his first policy speech since taking office, on Saturday warned of a “calamity” from the standoff over North Korea’s nuclear program unless a peaceful resolution is found quickly.

After his speech, Pyongyang issued a dispatch threatening that nuclear war could break out on the Korean Peninsula at “any moment,” an escalation of the communist North’s hostile rhetoric as international pressure grows for it to disarm.

On the eve of Roh’s inauguration Tuesday, North Korea fueled tensions by test-firing a missile into the sea off its east coast. Anticipating a second test, Japanese Deputy Cabinet Secretary Shinzo Abe said Saturday that Pyongyang may fire its long-range Taepodong ballistic missile toward the sea between Japan and the Korean Peninsula, Kyodo news agency reported.

The North’s official news agency also accused Washington of planning massive war games to prepare for an invasion, and said the country was “fully ready to repel the U.S. military attack.”

North Korea will take “a self-defensive measure when it thinks that the U.S. pre-emptive attack is eminent,” the agency KCNA said, without elaborating.

KCNA — the reclusive Stalinist regime’s bulletin board for the outside world — claimed an American RC-135 reconnaissance plane had intruded into North Korean airspace over its east coast almost daily since Feb. 21.

The U.S. military does not comment on such reports, said Stephen Oertwig, a U.S. military spokesman in Seoul. But North Korea’s east coast is dotted with guns and missile bases that U.S. intelligence officials believe can launch ballistic missiles.

The allegations of intrusions came as the United States and South Korea planned two joint annual military exercises on Tuesday through April 2 and March 19-26.

“These unceasing U.S. war drills drive the situation on the Korean Peninsula to such a dangerous pitch of tension that a nuclear war may break out on it any moment,” KCNA said Saturday.

Washington has repeatedly said it had no plans to invade North Korea.

On Saturday, 100,000 pro-U.S. demonstrators jammed a downtown Seoul plaza to support the presence of 37,000 U.S. troops in South Korea and condemn the North.

The demonstrators, many of them veterans in military uniforms who waved South Korean and U.S. flags, want the troops to remain to defend the South from a possible Northern attack.

In addition to the missile test, North Korea has reactivated a 5-megawatt reactor that could produce material for nuclear weapons, U.S. and South Korean officials said earlier this week.

South Korea sees Pyongyang’s recent maneuvers as aimed at forcing the United States into direct dialogue on a nonaggression treaty.

Washington has refused to hold direct talks unless Pyongyang abandons its nuclear programs and has ruled out a formal nonaggression treaty with Pyongyang, saying it has never signed such a treaty with any country.