In the countryside of North Korea, two men -- one Egyptian, one Chinese -- watch the still waters of a pool in a cold, nearly vacant building. Hundreds of silvery canisters sit in the clear water 30 feet below. Each contains highly radioactive metal that once fueled a power plant, metal that could be forged into the fearsome heart of a nuclear bomb.

The men re-run timed photos from poolside cameras, using a computer to detect changes in the image and confirm that nothing entered -- or left -- the water while they slept at a nearby dormitory. Assured, they make the rounds of other buildings, checking locks and seals on machinery and doors of the decrepit nuclear industrial complex.

They or their colleagues -- a new team is sent in about every six weeks from the International Atomic Energy Agency (IAEA) -- have been doing this chore at North Korea's Yongbyon nuclear plant 25 miles north of Pyongyang without interruption since Nov. 11, 1994.

But diplomats and analysts are worried that these international inspectors could be evicted from North Korea, and their crucial surveillance of the spent nuclear fuel aborted, following a decision by the United States and the other members of the executive board of the Korean Peninsula Energy Development Organization (KEDO). That decision would cut off future shipments of much-needed heavy fuel oil unless North Korea takes verifiable steps to dismantle a newly disclosed, separate program to enrich uranium for use in nuclear weapons.

President Bush, in a meeting with senior advisers Wednesday, decided to inform the other members of the KEDO board -- South Korea, Japan and the European Union -- that the United States will allow the current November shipment to be delivered but will not approve a December shipment unless North Korea takes the necessary steps. U.S. officials, who have closely consulted with allies in recent weeks, said they expect the other members to agree. A decision will be formally announced as early as today when the KEDO board meets in New York.

Under the 1994 Agreed Framework, KEDO is helping build nuclear power plants for North Korea in exchange for Pyongyang freezing operations at facilities capable of producing weapons-grade material and putting existing plutonium under inspection. The agreement also provides that 3.3 million barrels of oil are to be shipped to North Korea each year.

In the growing diplomatic standoff over the demand to end the uranium enrichment program, one of the biggest risks is that the nuclear fuel quarantined under international inspection after the last major nuclear row in 1994 could be freed up and made into weapons.

"If North Korea decides they want to really rattle sabers, they could expel the IAEA and threaten to reprocess the fuel. That would be a very serious situation," said C. Kenneth Quinones, who helped set up the inspection program in 1994.

If the oil flow is stopped, analysts and diplomats said, North Korea might evict the inspectors from Yongbyon. With some repair of the rusting infrastructure, the government could begin reprocessing the spent fuel rods from the pool into plutonium for atomic bombs in six to eight months, according to some estimates. The 8,000 spent fuel rods could conceivably make 30 or more atomic weapons, Quinones said.

"North Korea can quickly un-can the stored fuel rods to begin extracting plutonium, allowing it to build up a nuclear force far more quickly than would be possible through uranium enrichment," said Timothy Savage, a visiting fellow at Kyungnam University in Seoul.

North Korea also could unlock the IAEA seals on the old nuclear plant at Yongbyon, and, with a major overhaul, restart the Soviet-era reactor to begin churning out even more potential weapons fuel.

Before the U.S. decision on the oil was announced, a parade of U.S. officials who had come for consultations privately advocated stopping the shipments, and said Congress would do so next year anyhow.

But Japan and South Korea disagree; they have told the Americans that it would be a mistake to end the oil flow and the 1994 Agreed Framework under which the shipments were sent. They argue that move could prompt an escalation of brinkmanship by North Korea.

"Unless we find some better alternative, it's very risky for all of us to throw it away," said Katsunari Suzuki, in charge of the North Korean negotiations for Japan. "It's better than nothing."

There are gaps in perceptions, the Japanese Defense Agency head, Shigeru Ishiba, acknowledged in parliament Monday. He warned that U.S. pressure to halt the KEDO oil shipments could cause disarray.

And it may escalate North Korea's moves, others say.

"If America stops the oil shipments, North Korea will consider the 1994 Agreed Framework completely dead and will restart the nuclear program. Definitely," said Kim Myong Chol, the former editor of People's Korea magazine in Tokyo, who often reflects Pyongyang's line. "And if America imposes economic sanctions -- depending on the nature of the sanctions -- North Korea could regard that as an act of war."

Assistant Secretary of State James A. Kelly, the State Department point man on the issue, has said the United States will not negotiate with North Korea until there is "a complete and visible dismantling" of North Korea's uranium enrichment program.

The United States contends that a unified diplomatic front to isolate North Korea will force it to capitulate. But others who have dealt with North Korea for years say its traditional pattern is to increase the stakes, not to back down.

North Korea also has other cards to play, they point out.

The North's response might be as mild as halting the program under which the U.S. military has made regular trips to North Korea since 1996 to search for the remains of more than 8,000 American servicemen who died in the Korean War, an action it has taken twice before.

But North Korea could act more drastically and eject the 1,400 South Korean and Uzbek KEDO workers now pouring the concrete for the foundations of a light-water reactor power plant on the eastern coast under the 1994 pact.

"If they feel the United States is going to end the fuel shipments, they would most likely respond by evicting KEDO," said Quinones, speaking from Centreville, Va. Quinones said he believes that both sides will try to avoid an escalation of tensions. Both have shown some willingness to contain the confrontation, he said.

But the light-water plant is five years behind schedule, and North Korea may feel it will never get power from the completed project anyway, he said. North Korea has long protested that the United States and other KEDO countries failed to uphold their part of the agreement.

Evicting the IAEA inspectors and removing the spent fuel would considerably ratchet up the crisis. The Clinton administration was on the verge of ordering military strikes against North Korea in 1994 over just those sorts of preparations by Pyongyang after the IAEA detected possible diversions in its nuclear power plant fuel.

The most incendiary escalation of the stakes would be a test-firing of a long-range missile by North Korea, similar to one it launched in 1998 that alarmed Japan and its neighbors. North Korea warned last week that it may end its moratorium on such tests, adopted in 1999 as a gesture to the United States.

"North Korea could test-fire long-range missiles off the coast of Washington or New York in the Atlantic Ocean, and it would be legal under international law," Kim said. "It all depends on the American response. We're just at the beginning of a crisis. We're on a threshold."