The anniversary of the Korean War passed amid a worsening security crisis Sunday, with Japan warning of potentially crippling oil and food sanctions against North Korea if it carries out a long-range missile test.

South Korean President Roh Moo-hyun told war veterans that the North's apparent moves to launch a missile shows that security on the peninsula is "still volatile," but stressed that Seoul will continue reconciliation efforts.

Japanese Foreign Minister Taro Aso warned that Tokyo would consider the suspension of oil and food sales if the missile is launched, accusing the North of intimidation.

"All options are on the table," Aso said on public broadcaster NHK. "I believe public opinion would condone sanctions, even on oil or food."

The 56th anniversary of the still-unresolved war came amid alleged actions that analysts say would enable the North to test-launch a missile capable of reaching Japan and parts of the United States.

Both the U.S. and Japan have made clear that sanctions are an option if North Korea refuses to cooperate, and there has been speculation that the United States could try to intercept the missile with its fledgling missile defense system.

South Korea's Prime Minister Han Myung-sook urged the North to return to six-party nuclear talks as soon as possible, calling the nuclear issue "the biggest security threat" to the South.

The talks include both Koreas, Japan, the United States, China and Russia and have been deadlocked since November.

"North Korea should fully recognize concerns of the international community and should resolve this issue soon," Han said during a war anniversary ceremony.

North Korea meanwhile vowed to repel any invasion by the U.S., which the North claims launched the 1950-53 conflict.

"If the U.S. imperialists set another fire of war ... our army and people will finally settle our battle with the U.S. by mercilessly crushing and sweeping out the aggressors," the North's Rodong Sinmun newspaper said in a commentary, carried by the official Korean Central News Agency.

Intelligence reports say fuel tanks have been seen around a missile at the North's launch site on its northeastern coast, but officials say it's difficult to determine from satellite photos if the rocket is being fueled.

In Washington, the Pentagon's missile defense chief, Gen. Henry A. Obering III, said he has little doubt that U.S. interceptor rockets would hit and destroy a North Korean missile on a flight path toward U.S. territory if President George W. Bush gave the order to do so.

In New York, U.S. Ambassador to the United Nations John Bolton said the U.S. had approached the North Koreans last weekend "and told them that we thought the idea of a launch was a very bad idea."

Pyongyang has said it is willing to talk to the United States about its missile concerns, repeating its long-held desire for direct meetings with the Americans. Washington, however, has refused, insisting it will only meet the North amid six-nation talks, deadlocked since last November.

Aso said Sunday that the North's brinkmanship would not help it reach its goal of direct negotiations with Washington.

"How can you put up a rocket and then demand talks? That's intimidation, and makes it most difficult for America to engage in talks," he said.

The Korean War ended in a cease-fire, not a peace treaty, leaving the two Koreas technically at war.

The North's moves on a possible missile launch have drawn widespread international concern. Even its main allies, China and Russia, have issued warnings.

South Korean Foreign Minister Ban Ki-moon, who visits Beijing Monday for talks that would likely focus on the missile concern, said that he would " ask China to actively persuade North Korea," according to the South's Yonhap news agency.

China, a key provider of aid to the impoverished North, is believed to be the only country that has considerable leverage over Pyongyang.

The North shocked the world in 1998 by firing a missile that flew over northern Japan and into the Pacific Ocean. It has been under a self-imposed moratorium on long-range missile tests since 1999, but has since test-fired many short-range missiles.