Once a month, Hiroshi Yano bundles together a few million yen, wraps the money in plastic with a Japanese customs seal, and puts it on a ship to be handed over at sea to a boat captain from North Korea and delivered to the Stalinist government there.

It's all legal: The money is payment for North Korean snow crabs that Yano imports for Japanese tables. And Yano said he wants to continue the business, nukes or no nukes.

"We are just a private company doing trade. We are independent of politics," said Yano, manager of an import business that runs three ships to North Korean waters from this port town 350 miles west of Tokyo.

The payments are just one example of the many flows of money and goods that prop up the North Korean system and circumvent the isolation that the United States and other countries have sought to impose.

The Bush administration's strategy to tighten that isolation and compel North Korea to dismantle its nuclear weapons program may be undermined by the complexity and number of trade routes that snake in and out of North Korea.

The trade ranges from the global export of missiles to lone Korean smugglers who wade the river border into China to barter for food. It includes products as legal and innocuous as Yano's snow crabs and as dangerous as smuggled drugs delivered to Japan's coastline by unmarked ships.

The United States has said it will not ask the U.N. Security Council for economic sanctions, which the government in the North Korean capital, Pyongyang, has said it would consider "tantamount to war." But with no plausible military option, U.S. officials have said they will likely want to tighten an economic and diplomatic noose around the government.

"If North Korea continues to pursue its nuclear weapons program, they are going to end up in some kind of self-containment," a senior U.S. official said recently. "The world is not going to deal with them."

But some countries might disagree. Each year, North Korea makes missile sales estimated to bring in anywhere from several hundred million dollars to $1 billion. Its customers, which intelligence agencies say include Libya, Iraq, Iran, Yemen and, in the past, Pakistan, are not all sympathetic to the U.S. point of view.

Even Washington's allies may undermine the effort. In recent years, South Korea has slowly warmed its ties and increased cultural and business exchanges with North Korea -- contacts nourished by bribes and contract padding, according to analysts and an entrepreneur with experience dealing with North Korea.

"To get a North Korean performing [arts] company to come here, for example, you put $40,000 or $50,000 extra" in the contract, said one analyst in Seoul, asking not to be identified.

Political opponents of South Korea's president, Kim Dae Jung, say that even his historic summit in Pyongyang in June 2000 was preceded by an infusion of cash.

On Thursday, government auditors confirmed that the Hyundai conglomerate, which has been closely tied to Kim's policy of rapprochement with North Korea, borrowed $186 million from a government-run bank shortly before the summit and used it for unclear purposes in the communist state. Kim's aides have denied the money bought the summit.

Hyundai has aggressively sought business in North Korea, rejecting criticism that its deals bolster an aggressive government.

"We made clear and told them half-jokingly not to use the money in making missiles," Kim Yoon Kyu, president of Hyundai Asan, Hyundai's North Korean development arm, said in an interview in Seoul last week. "I asked them where they used the money from us. They said they can't tell us the details, but they sure didn't use the money to make missiles."

None of North Korea's closest neighbors -- South Korea, China, Japan or Russia -- has welcomed Washington's isolation strategy, and each allows its citizens to visit the North and spend money there.

In 2001, about 8,500 South Koreans traveled to North Korea, spurred by a boom in academic, cultural and trade exchanges and reunions of families long separated by the Korean War. Thousands more tourists traveled to Mount Kumgang, in eastern North Korea. Tour buses filled with Chinese are a routine sight in Pyongyang. And about 3,400 travelers from Japan went to North Korea last year. About half went aboard a ferry named Man Gyong Bong, which sails from Niigata in Japan to Wonsan in North Korea 20 to 30 times a year.

Here in Sakaiminato, a port and fishing town of 37,000 residents on the Sea of Japan, three hulking North Korean cargo ships were docked at the snow-blown pier last week. The rusting old vessels, hand-me-downs from the Japanese fleet, had arrived with their holds filled with tubs of red snow crabs.

The importers pay the North Koreans with bundles of cash or with bartered goods -- blankets, food, sports shoes or a bike for the sailors, or generators and used cars for the boats' masters. A luxury 10-year-old Toyota Crown that will probably be pressed into service in the North as a limousine for VIPs will go for about 30,000 large crabs, worth about $4,000.

Seafood is the biggest component of Japan's $370 million annual trade with North Korea, which brought the communist state's ships to Japan 1,200 times last year. South Korea ran up $350 million in trade with its northern neighbor, much of it by sending textiles to North Korea and buying back finished clothes. China reported that its trade boomed to $730 million last year.

At the Chinese border, "the trucks are lined up on the North Korean side as far as you can see," said Dong Young Seung, the chief North Korea researcher at Samsung Economic Research Institute in Seoul. "They are going in empty, buying whatever they can in China. Anything they get, they can sell in North Korea." And that's only the legal trade. Smugglers have long plied the porous border.

"It used to be food and oil," said a smuggler based in the Chinese city of Yanbian, who runs a multimillion-dollar-a-year business out of a teahouse there. "Now, with the North's official economy in collapse, it's everything from pots and pans to shampoo and soap and underwear."

Many intelligence analysts say they believe that other smuggling is orchestrated directly by powerful officials in North Korea. Japanese police say the North sends out illegal methamphetamines, and that trafficking that has been increasingly busy in the last six years. Authorities have made six large busts traced to North Korea in that period, finding the stimulants hidden in honey cans, concealed in bags of shellfish or being handed over in packages at sea.

Last year, Japanese salvage teams raised a vessel that sank during a skirmish with Japanese patrol boats on Dec. 22, 2001. Japanese officials say it was North Korean and was the same ship photographed smuggling drugs to Japan in 1998. Officials suspect it was on a similar mission when it went down.

"We can't say for sure it is the North Korean government doing it," said Naoto Takeuchi, head of the drug division of Japan's National Police Agency. "But it's someone in North Korea with organization, capital and technique."

North Korea has persistently sought to import large quantities of ephedrine, the main component of methamphetamines, saying it was needed for cold medication. Twenty tons of the chemical, enough to make 10 years' worth of cold medication for North Korea, were seized in 1997 while reportedly en route there, according to the United Nations' International Narcotics Control Board.

Still, the finished drugs get through to Japan, and traffickers there pay the North for the product. In November and December, packages containing 500 pounds of methamphetamines floated ashore in Japan. Periodically, bodies bearing pins of North Korean leader Kim Jong Il wash up on Japanese beaches -- the result, authorities suspect, of a smuggling or infiltration trip run awry.

Economic links with Japan and technology transfers to North Korea are openly promoted by pro-Pyongyang ethnic Koreans who live in Japan. Their community association, called Chosen Soren, has as members an estimated 200,000 of Japan's 630,000 Korean residents. At the height of Japan's bubble economy in the 1980s, intelligence analysts say, Chosen Soren members were sending millions of dollars a year to the North.

And Korean-run credit unions in Japan siphoned depositors' money, created ghost accounts and made fraudulent loans to send billions of dollars to North Korea, Japanese investigations have concluded. That scheme collapsed, ending in a string of arrests in 2001. The credit unions went bankrupt, and the Japanese government reluctantly repaid depositors in an $11 billion bailout.

Analysts estimate the cash from Chosen Soren has dwindled to a trickle. But myriad other connections help take the sting out of isolation for Pyongyang. Those links "may seem like small change now," said a Hyundai official, Shim Jae Won. "But if this grows bigger, it will have an enormous effect. With all these projects going on in their territory, war won't make sense."

Special correspondent Joohee Cho in Seoul, staff writer John Pomfret in Yanbian, China, and special correspondents Akiko Kashiwagi and Sachiko Sakamaki in Tokyo contributed to this report.

Hiroshi Yano pays millions of yen each month for snow crabs he imports from North Korea.North Korean cargo ships like this one docked in Japan 1,200 times last year, contributing to trade worth $370 million.