Inside a Starbucks coffee shop tucked in a posh shopping district of South Korea's capital, three women in their late twenties sip cappuccino, their Prada purses and Gucci sunglasses testifying to lives of comfort in the southern half of the Korean Peninsula -- the side defended by 37,000 U.S. troops.

Yet, as their conversation turns to the nuclear confrontation playing out here, all three express sympathies for North Korea and anger toward the United States. They reject the central tenet that has bound South Korea and the United States together for a half-century -- that they need American troops here to protect them from the menacing Communist power to the north.

"If the United States left, I wouldn't mind," says Kim Young Ran, 29. "If North Korea wants nuclear weapons, I think they should have them. The U.S. and so many other countries have them. There's no way North Korea will attack us with their nuclear weapons. I don't think so. We're the same country. You don't bomb and kill your family. We share the same blood."

That refrain, heard here with increasing frequency, largely explains the gulf between South Korea and the United States as the two countries digest the possibility of North Korea arming itself with nuclear weapons. It also highlights the enormous obstacles confronting the Bush administration as it seeks to assemble a united front to force North Korea to reverse course; South Korea's support is critical to any attempt to isolate the North.

In a recent opinion poll conducted by Korea Gallup for the Chosun Ilbo, one of South Korea's three major newspapers, more than 53 percent of South Koreans surveyed said they disliked the United States, up from 15 percent in 1994. Over the same period, the percentage of those who said they liked the United States fell from nearly 64 percent to 37 percent.

Many analysts say the growing anti-Americanism here has emboldened North Korea's leader, Kim Jong Il, to ratchet up the confrontation because he is secure that the Bush administration cannot wage war against him, or even contain him, without the support of South Korea, and equally secure that such support is lacking.

"It wasn't like that back in 1993 and '94," said Lee Chung Min, a North Korea expert at Yonsei University in Seoul, referring to the last nuclear crisis here. "We thought North Korea was crazy and had no illusions about who they were building their bombs for. Now, Kim is less likely to bend, because he can count on South Korea. And that's a weird situation."

In the latest sign that North Korea is seeking to exploit this dynamic, the insular country today released a statement calling on the two Koreas to "pool their efforts and condemn and frustrate the U.S. nuclear policy for aggression," which it said was part of a larger "U.S. strategy to dominate the world." It accused the United States of "working hard to bring a holocaust of a nuclear war to the Korean nation."

[On Thursday, the Reuters news agency, citing the South Korean Unification Ministry, reported that North Korea had proposed going ahead with minister-level talks with South Korea on Jan. 21-24.]

The poll numbers revealed a striking generational divide. While only 26 percent of South Korean respondents age 50 and over expressed dislike for the United States, the rate for those in their twenties was over 75 percent.

Analysts explain this shift by noting that older South Koreans have memories of the 1950-53 Korean War and feel an uneasy proximity to the artillery and missiles lined up on the other side of the Demilitarized Zone that divides the peninsula. Those in their twenties, on the other hand, grew up in a country that felt stable and increasingly prosperous, far removed from threats of war and poverty.

"They have naive and romantic thoughts about the North," said Kim Tae Woo, a conservative arms control expert at the Korea Institute for Defense Analyses in Seoul. "They think we are one people, North and South, and we should be reunited. They simply don't see the military strength the North has created."

Young people say they are freer than previous generations to think critically about inequalities in South Korea's relations with the United States.

"Our parents only had monopolized and controlled information fed to them by the government, but we get information from all sorts of places," said Chang Hye Jin, 33, a software developer. "The Internet changed a lot. We express and discuss many issues in the chat rooms. Through that, we get a lot of different ideas."

Anti-Americanism is hardly new here. During the 1980s, radical students engaged in violent protests against the authoritarian regime of Chun Doo Hwan and lashed out at the United States for complicity in the government's repressive policies. More recently, activists have decried what they see as environmental pollution linked to the presence of U.S. troops here. But those who have watched such events unfold say there has been a palpable, fundamental shift in attitude.

"Anti-Americanism is getting intense," said Kim Sung Han, a fellow at the Institute for Foreign Affairs and National Security, a research group in Seoul associated with the Foreign Affairs Ministry. "It used to be widespread and not so deep. Now it's getting widespread and deep."

The 1980s radicals have been joined by a new crop of people in their twenties and thirties who are less anti-American than they are pro-Korean. Reared on textbooks that portray North Korea not as an enemy but as a brother, many have come to see the U.S. military presence as an impediment to reunifying the two halves of the peninsula. "I don't think the United States understands that we are one country," said Kim Young Jin, 34, a gray-suited banker.

This shift has profoundly altered relations between South Korea and the United States. Through the Cold War and the last decade, governments in Washington and Seoul danced in lockstep. But that changed under the rule of South Korean President Kim Dae Jung, whose "sunshine policy" toward the North has relied upon engagement and reconciliation, expanding trade and aid while reuniting families divided by the Demilitarized Zone.

While Bill Clinton was in power, the sunshine policy caused no discord. But when President Bush came into office and branded North Korea part of an "axis of evil," along with Iraq and Iran, it embarrassed Kim and caused a cleavage in Seoul's dealings with Washington.

Other incidents have further inflamed tensions. During a speedskating race at last year's Winter Olympics in Salt Lake City, a South Korean entrant, Kim Dong Sung, crossed the finish line first, but was disqualified. He yielded the gold medal to American Apolo Anton Ohno, and people here charged foul play.

Last June, a U.S. Army vehicle fatally crushed two South Korean teenage girls during a training exercise. When a military court subsequently acquitted two soldiers of negligent homicide, it provoked a string of protests that have continued.

In downtown Seoul, a sign went up in a restaurant declaring that Americans were not welcome. School bags began sporting "Anti-American" buttons. On major shopping streets, activists using bullhorns began proclaiming "Yankees go home."

Last month, South Koreans elected a new president, Roh Moo Hyun, who advocates continuation of the sunshine policy. During the campaign, he caused an uproar when he said South Korea should not automatically adopt the side of the United States if there is conflict with the North.

After the election, Roh met with military officials and instructed them to draw up plans that assume a reduction in U.S. forces stationed here. That has occasioned much speculation in the local press that Roh, who takes office Feb. 25, may ask the United States to reduce its troop presence -- an outcome feared by conservatives here.

"Roh and his people have no concept of security," said Kim Tae Woo, the conservative defense expert.

Today in Pyongtaek, outside a U.S. air base, several hundred South Koreans, many of them local shopkeepers, rallied to oppose calls for a withdrawal of U.S. troops.

Much has been made here about the fact that Roh speaks no English and has never visited the United States. Despite his strained ties with the United States, Kim Dae Jung lived there for years in exile in the days of repressive government. He has called on those demonstrating against the acquittal of the U.S. soldiers to halt their protests.

Those close to Roh say it would be wrong to paint him as holding anti-American views. He wrote a book about Abraham Lincoln, whom he considers his role model. While Kim Dae Jung has his prestige invested in a series of economic projects with the North -- a giant conference center, rail links, a tourism site -- Roh could use them as bargaining chips to force North Korea to pull back from the nuclear brink.

"They were not initiated by Roh, therefore he can take much freer action," said Moon Jung In, a North Korea expert at Yonsei University who has served as an informal adviser to the president-elect. "He might be much tougher on North Korea if they don't cooperate. Roh has been badly misunderstood."

Antipathy toward the United States is strong among younger South Koreans, such as these students protesting Saturday near the U.S. Embassy in Seoul. The U.S. military presence in South Korea was the focus of flag-burning protesters in Seoul on New Year's Eve. Such protests have continued.