As leaders in South Korea feared a new long-range missile test by Pyongyang, President Bush's spokesman, Tony Snow, told FOX News on Sunday that the U.S. expects North Korea to honor its 1999 self-imposed moratorium on nuclear missile testing.

"We expect them to maintain the moratorium," Snow told Chris Wallace on "FOX News Sunday."

"We do not want to have a missile test out of North Korea," he said. "But right now, at least the news today — the Japanese government has announced that, at least to the best of its knowledge, that there's not going to be a launch today, and we hope there's not going to be a launch."

North Korea vowed Sunday to increase its "military deterrent" to cope with what it called U.S. attempts to provoke war, amid signs the country was preparing to test a long-range missile that could reach the continental United States.

Meanwhile, Japan said it would file a "fierce" protest and seek an immediate U.N. Security Council meeting if the North test-fires what is believed to be a Taepodong-2 missile.

There was no mention of a missile in a report from North Korea's official media on a national meeting marking the anniversary of leader Kim Jong Il starting work in the country's communist party.

North Korea has not fired a long-range missile since August 1998, when it sent a rocket flying over parts of Japanese territory in a launch that shocked the region.

But signs of a launch have grown in recent days, with reports saying a missile has been assembled at a launch pad on the North's eastern coast and may have been fueled for launch.

"There are signs" of a missile launch, Jung Tae-ho, a spokesman at the South Korean president's office, told The Associated Press, without elaborating. He said security officials were "closely watching the situation."

South Korea's Yonhap news agency, citing a South Korean government official, reported that the weather around the North Korean launch site was bad, indicating the North may not fire its missile Sunday.

Satellite weather images posted on the Web site of the South's Korea Meteorological Administration showed clouds around the launch site in northeastern North Korea as of early evening.

A missile launch "depends a lot on weather conditions," a South Korean intelligence official told The Associated Press. A nighttime launch is considered unlikely.

Japanese Foreign Minister Taro Aso said his country would not immediately resort to arms if North Korea fires a missile but would take the issue to the United Nations.

"We will naturally file a stern protest and it will be fierce," Aso said on TV Asahi, adding that the North would gain nothing from the test.

Aso also reportedly said it would be "inevitable" that the Security Council would consider imposing sanctions on Pyongyang if it goes ahead with the missile launch.

Speaking on Fuji TV, Aso said Tokyo could impose sanctions on the North in the event a missile launch because that would violate Pyongyang's commitment to impose a moratorium on such tests.

At the North Korean national meeting Sunday, officials talked about increasing the North's "military deterrent" — a phrase commonly used by the country to refer to its nuclear program, which Pyongyang contends it needs for a defense to a possible U.S. attack. Washington denies any intention to invade.

"The [North] Korean army and people will do their best to increase the military deterrent with sharp vigilance to cope with the moves of the U.S., which is hell-bent on provocations for war of aggression on the DPRK, resorting to its anti-DPRK policy, and its followers Japan and other bellicose forces," said Choe Thae Bok, secretary of the Central Committee of the Workers' Party of Korea, according to the Korean Central News Agency.

DPRK refers to the Democratic People's Republic of Korea, the North's official name.

"If the enemies ignite a war eventually, the Korean army and people will mercilessly wipe out the aggressors and give vent to the deep-rooted grudge of the nation," Choe said.

The United States and Japan have confirmed that the assembly of what is believed to be a Taepodong-2 missile has been completed with two stages at the launch site, based on photos from satellites, Japan's largest daily, the Yomiuri newspaper, reported Sunday.

The Taepodong-2 missile is believed to be the North's most advanced model with the capability to reach the United States with a light payload.

The paper also said it appeared North Korea has begun filling the missile with fuel, citing unidentified U.S. government officials who conveyed information Saturday to the Japanese government through unofficial channels.

Yonhap, citing diplomatic sources in Washington, also reported there was a possibility the missile already may have been fueled, with satellite photos showing tens of fuel tanks at the launch site.

The missile concerns come amid an extended impasse at the six-nation talks on the North's nuclear weapons program. The talks — involving the United States, the two Koreas, China, Japan and Russia — were last held in November.

The North has claimed it has a nuclear weapon, but it is not believed to have a design that would be small and light enough to place on top of a missile.

The Associated Press contributed to this report.