To street protesters in the South Korean capital, American beef is a menace to be feared — and stopped.

Shin Hae-suk, a 54-year-old housewife, is convinced that if South Korea resumes importing U.S. beef, the U.S. will send South Koreans meat at higher risk of mad cow disease. "What if my child eats dangerous beef in a restaurant?" she asked.

Shin's views on American beef — which South Korea banned in 2003 after the first U.S. case of mad cow disease was discovered in Washington state — may seem odd to Americans, who wolf down steaks and hamburgers produced from domestic cows.

But in Seoul, such anxieties have spurred near daily street rallies that have humbled South Korea's new president and forced his government to delay carrying out a deal with the U.S. to resume imports.

Fears have been fanned largely by a sensational television report last month and Internet chatter about the meat, which both governments have repeatedly said poses no health risk. Rumors have circulated that U.S. meat packers plan to dump beef from older cows — considered at higher risk for mad cow — on the South Korean market.

A belief that the South Korean government is sacrificing safety to curry favor with Washington and perceptions of arrogance on the part of President Lee Myung-bak have also spurred anger.

A crowd estimated by police at about 3,000 people gathered Wednesday night to denounce the beef import plan and call for the ouster of Lee — who only took office in February.

Protests, occasionally reaching 10,000 people, have been for the most part peaceful, even festive, affairs characterized by singing, chanting and speeches at a popular gathering place in downtown Seoul.

Many of the participants have been university students, though the rallies have attracted others as well.

Tensions, however, have risen markedly the past few days as police arrested more than 200 people after protesters spilled onto the streets. Some were even beaten by riot police during scuffles. Dozens of the detained have been released.

The root of the problem goes back to December 2003 when the first case of mad cow disease in the United States was discovered in a Canadian-born cow. Two subsequent infections were found for a total of three to date.

Scientists believe mad cow disease, or bovine spongiform encephalopathy, spreads when farmers feed cattle with recycled meat and bones from infected animals. In humans, eating meat products contaminated with the cattle disease is linked to variant Creutzfeldt-Jakob disease, a rare and fatal malady.

After protracted talks, limited imports of beef from U.S. cattle less than 30 months of age briefly hit supermarkets last year in South Korea, formerly the third-largest export market for U.S. beef. But they were soon halted when banned items such as bones and bone fragments were discovered in some shipments.

Then last month, the two countries announced just hours ahead of the start of a summit in the United States between Lee and President Bush that the issue was resolved and U.S. imports would finally resume.

Case closed? Far from it.

A popular current affairs TV program with a reputation for muckraking went on the air about 10 days later, questioning the safety of U.S. beef and claiming Koreans are more susceptible to the disease that can result from eating mad cow-infected beef.

South Korean medical officials who appeared at a press conference with the agriculture minister denied the claims. But days later, 10,000 people gathered for a candlelight protest and the movement was up and running.

Though relatively small compared to major protests in recent years — such as one that drew 50,000 people to downtown Seoul in 2004 to oppose moves to impeach then President Roh Moo-hyun — the fact the demonstrations refuse to die out has the government on the defensive.

Lee went on television last week to apologize for not having gained public understanding. The government has at least twice delayed taking the final administrative step required for imports to resume.

Some have grown weary of the clamor and are calling for the nation to move on.

"Actions by these people may be effective in shaking this government, but are not conducive at all to reviving the economy and stabilizing state affairs and livelihoods, which most of the people want," the Dong-a Ilbo newspaper said in an editorial Monday.

Suspicions the openly pro-American Lee was too eager to give in to Washington on the beef issue to help ensure passage of a bilateral free trade agreement, under fire from members of Congress in U.S. beef-producing states, have not helped.

The office of U.S. Trade Representative did not immediately respond to a request for comment on the matter.

Indeed, Lee's image — that of a can-do former businessman that helped him win office by a landslide — has taken a hit, with his approval ratings falling sharply amid the view he has behaved arrogantly.

"Lee ruled us as if he was a CEO and his people were employees," said Oh Se-young, a 43-year-old software company worker.