It has become a bit of a parlor game here in the South Korean capital: guessing whether North Korea will test-fire a new long-range missile.

"We have a bet," confided a top staff member in the presidential Blue House, pointing out a colleague. "I say yes; he says no."

The question is puzzling leaders from Washington to Tokyo to Seoul, and the outcome may have a seismic effect on North Asia.

U.S. interest is high because of predictions that the missile, the Taepodong II, might have the range to reach Alaska or Hawaii--and that the next advance in Pyongyang's rocketry could reach the continental United States. The Pentagon said Tuesday it is positioning two Navy observation ships to watch for the launch.

The head of South Korea's National Intelligence Service, Chun Yong Taek, said at a parliamentary hearing in Seoul today that North Korea has finished making the missile parts and that it would take at least three weeks to transport and assemble them for launch.

"North Korea appears to be weighing possible economic and political losses and gains," Chun said, according to reports from the closed hearing.

What all the parties have done is raise the stakes, and the betting here overall is that North Korea will look at the score card and decide not to fire the test missile. The most common explanation is that North Korea hopes its threats to go ahead will pressure other nations to provide greater economic assistance. That worked in 1994 and again this year, when Pyongyang got additional aid in return for stopping nuclear development that U.S. experts feared could lead to a weapons program.

"By threatening, acting irrational, they've been able to get a lot of concessions. Why should they stop that pattern?" asked Lee Jung Hoon, chairman of the Department of International Studies at Yonsei University.

But the tactic is wearing thin. The Japanese, and many in the U.S. Congress, are growing impatient at being pushed to the brink. Judging from their comments, the threats have built up so much that the balance is tipped: North Korea stands to lose all it won if it fires the missile.

"All of the aid must be halted if they fire again--even the humanitarian aid," said Yoo Jay Kun, a national assemblyman in Seoul and close adviser to President Kim Dae Jung.

Efforts to discourage North Korea from the test have included carrots and sticks, but so far neither has had success. The North Korean government has repeated that it has a sovereign right to fire what it describes as a rocket to launch satellites and warns that the more pressure it gets the more likely it is to go ahead.

The concern is not to prevent an immediate threat--the missile would fall harmlessly somewhere in the Pacific. But the test would subtly but significantly change relations that keep this region stable.

Japan, which for five decades has maintained a determinedly pacifist stance to atone for wartime militarism, now is talking about getting spy satellites, antiballistic missiles and bomber refueling planes, and is mulling over changing its "peace constitution."

Such talk worries its neighbors, including China and both Koreas, who remember Japan's zealous military ambitions and brutal occupations. China is grumbling about Japan. South Korea, historically held in check by the United States, now wants U.S. approval for its own long-range missiles. And the Clinton administration, which has twice defused showdowns with North Korea through negotiations, sees its success unraveling if the test-firing goes ahead.

"I think the United States and Japan have fallen into North Korea's trap. The U.S. doesn't have any policy options at all other than reacting to North Korea," said Kim Hyung Kook, who directs the Center for Asian Studies at American University and is in Seoul doing research.

By the Western score card, a missile test would harm North Korea. It would halt work on the power plants being built in North Korea by the United States, the European Union, Japan and South Korea as part of the 1994 agreement. It would likely end or reduce much of the food and humanitarian assistance from Japan and South Korea.

South Korea could stop its tourism project to the North that is supposed to provide North Korea with almost $1 billion in five years. Japan could cut off the hard currency flow from Koreans living in Japan. The test would spur new military acquisitions by Japan and South Korea. It would displease China, North Korea's sole ally in the region, and Russia to its north.

"What's the grand strategy of North Korea? If it's extracting concessions, I would have to say that a package deal would get them more than firing off a missile," said Lho Kyong Soo, professor of international politics at Seoul National University.

But Cho Myung Chul believes the North Koreans use different calculations from those in the West. As he tells it, what seems perplexing to the rest of the world is perfectly understandable within the closed, isolated country of 22 million people.

Cho should know. He was a member of North Korea's ruling class, the son of a cabinet minister, a promising academic who, he says, knew leader Kim Jong Il well until 1994, when Cho slipped away from a conference in Beijing and defected to South Korea.

"North Koreans have the idea that the United States will attack them. They truly believe that," Cho, 41, said in his book-lined Seoul office, where he now studies his old homeland for a government sponsored think tank, the Korean Institute for International Economic Policy.

The government uses that fear to rally the populace, whipping up intense passions in the process, and to justify shortages, he said. When a test launch of the Taepodong I missile last August startled the United States and Japan, there was jubilation in the streets, said Cho, who closely studies news and intelligence reports from the North.

"The public says, 'We have starved and worked hard, but look, we have achieved this great, good thing,' " Cho said. That source of pride, in a nation in which "self-reliance" is almost a religion, encourages sacrifices, he added. "Nobody in North Korea would say, 'Don't fire this missile, and instead give us food.' That's just not their mentality."

CAPTION: South Korean intelligence chief Chun Yong Taek, right, told a parliamentary committee that the North appears to be weighing the pros and cons of launching its new missile.

CAPTION: The test launch of North Korea's Taepodong I missile last August startled the United States and Japan, but there was jubilation in Pyongyang's streets, a North Korean defector says.