BARCELONA, Spain -- Tobacco began its conquest of the Old World right where a bunch of teenagers, basking in the Mediterranean sun the other day, encountered the 21st century's latest weapon against smoking.

Out came the cigarette packs, and two of the nonsmokers, eyeing the bold new health-warning labels that debuted in Europe last month, began loudly scolding their friends.

"Look, there, 'Smoking can cause a slow and painful death,'" said one of the girls.

Another grabbed a half-empty pack from a boy and pointed, "And there, 'Smoking causes fatal lung cancer.'"

Adults gathered and joined the clamor, right under the towering statue of Christopher Columbus that commemorates the explorer's 1493 return from his first voyage to the New World. This is where Columbus landed with the first tobacco seeds ever to reach European soil, which Spanish farmers promptly began to plant.

Europeans have been smoking like chimneys ever since, and few outdo the Spanish, who have logged one of the continent's highest rates of smoking per capita. But they're trying to stop.

So the European Union and governments around the world are turning to stronger, in-your-face warning labels to discourage smoking. Yet the United States, which pioneered tobacco warning labels in 1965, hasn't upgraded its cautions since 1984.

"Worn out" is how the Federal Trade Commission described them in a report to Congress as far back as 1981. A National Academy of Sciences expert panel repeated that phrase in a 1994 major study.

Canada started the bolder trend with explicit labels beginning in December 2000. Thailand, Brazil and Australia are among countries that have since jumped onto the bandwagon. Under a tobacco-control treaty the World Health Organization adopted in May, warning labels covering 30 percent of each cigarette pack would become the minimum world standard.

The 14 new warning labels made mandatory in all EU countries meet that standard. They appear in bold type on the front and back of both individual packs and cartons, and graphic color photographs will debut next October, featuring cancerous lungs, diseased gums, damaged hearts and other tobacco carnage.

"We have to find new and innovative ways to illustrate the shocking truth that half of all smokers will be killed by their habit," said EU Health Commissioner David Byrne. "One hard-hitting picture really does speak more than a thousand words."

Many health experts regard the warning labels on tobacco in the United States as far less effective than their more recent counterparts elsewhere in the world. U.S. warnings, they note, are small (covering less than 20 percent of a pack), vague, impersonal, rendered only in text and placed in a barely noticeable spot on the packs' sides.

"It's hard to remain in denial when the cover of the pack reminds you of the wreckage cigarettes are causing to your body," Dr. Michael Thun, the American Cancer Society's chief of epidemiology research, noted in an interview.

The United States is gaining a global reputation as backward for sticking by its old labels. "The U.S. was the first country in the world to introduce health warnings," Luk Joossens, a Belgium-based consultant to the International Union Against Cancer, noted in an interview. He then added: "But the actual American health warnings were introduced in the previous century and are now a part of history."

Joossens, who helped to craft the new European labels, said, "The U.S. should certainly consider having health warnings similar to the EU."

Doing so literally would take an act of Congress. In the three major laws establishing cigarette warnings, Congress never delegated authority to update the labels to the FTC or any other federal agency.

The first law, the Federal Cigarette Labeling and Advertising Act of 1965, set the pattern. Congress specifically prevented federal agencies and individual states from imposing tougher warnings. It also barred states from imposing "any requirement or prohibition based on smoking and health" on cigarette advertising.

The National Academy of Sciences has concluded that public health took a back seat to politics when those label laws were drafted due to prominent tobacco-state lawmakers' concerns about damaging their home-state industry. While giving a nod to public health, the laws temporarily shielded the tobacco industry from product-liability lawsuits brought by injured smokers. They also protected the tobacco makers from state regulation that might have meant bolder warning labels or other restrictions.

Do warning labels work? No major, scientifically valid study has ever been conducted seeking to answer that question, and the National Academy of Sciences concluded that such a study probably would be impossible because researchers could never reasonably separate the effects of warning labels from those of other anti-smoking data.

But there's a broad consensus among experts that warning labels do discourage smoking to some extent, and there's almost universal agreement that bigger, bolder labels work even better.

"The more conspicuous and explicit they are, the better individuals will understand them," said Bethany K. Dumas of the University of Tennessee.

Dr. David M. Burns of the University of California-San Diego cited Canada's package warnings as an example. "The Canadian labels are both larger and more graphic, and the consensus is that they are more effective communication," he noted.

The Canadian labels cover half of the front and back of each pack and include 16 different text warnings. There are also full-color pictures that include a cancerous lung, a damaged heart, a brain after a stroke and a diseased mouth. Next to one image of a limp, drooping cigarette is this explicit message: "Cigarettes may cause sexual impotence due to decreased blood flow to the penis. This can prevent you from having an erection."

In 2002, researchers for the Canadian Cancer Society found that the big, picture-based labels were having an impact. A study of 2,000 adults found that 90 percent of smokers noticed the warnings. About 44 percent said the new warnings increased their desire to quit, 43 percent said they were more concerned about health hazards from smoking, and 38 percent of those who tried to quit cited labels as a factor. Almost half of nonsmokers said the labels reinforced their decision not to smoke.

Labels do more than inform and warn individual smokers, said Pennsylvania State University's Department of Marketing chairman, Dr. Marvin Goldberg. "They constrain the use of the packages as a marketing vehicle," he said.

Canada's legislation also required a package insert containing health information, including tips on quitting. The EU law does the same. Studies by Canada's national health agency show that cigarette packs now rival TV as the No. 1 source of information about the adverse health impact of smoking.

Studies by the U.S. Centers for Disease Control and Prevention and other organizations have found that U.S. smokers and nonsmokers both favor larger, picture-based warning labels.

Legislation calling for updated warning labels for tobacco products sold in the United States has been introduced in the last several sessions of Congress but has never reached a floor vote.