Jesse Ventura is no longer governor of Minnesota. But he is still pushing an agenda - in this case, sports betting over the Internet.

Ventura is the new spokesman for BetUS.com, a Web site operated from Costa Rica that lets people wager on sports contests from their home computers. "This is a step toward bringing something above board that clearly many people want to partake in," Ventura said.

In a sign of an increased acceptance of Internet gambling, online casinos in recent months have signed endorsement deals with a group of celebrities, including Tom Arnold, the actor; Brooke Burke, a model turned television host; and Jim Kelly, a former National Football League quarterback for the Buffalo Bills.

But there is a big potential catch: these stars and others who profit by promoting offshore casinos could be putting themselves in legal jeopardy. The government considers these Internet sports betting sites to be violating American law by providing unlicensed gambling on domestic shores.

The government has said in the past that it could prosecute Americans who promote and assist such foreign operations.

"There's a good chance they are criminally liable for the crime itself," said I. Nelson Rose, a law professor at Whittier Law School in California and the author of a book called "The Law of Internet Gaming." For celebrities who draw attention from law enforcement officials, he said, "the downside danger is enormous."

The Justice Department declined to comment for this article.

For his part, Ventura said he was not aware that federal law prohibited Internet gambling operations; his management company, he said, told him that the deal would not be a problem.

But Ventura also counters with a populist message that says, in essence, that millions of Americans who gamble online cannot be wrong.

And in that regard, the relationship between casinos and celebrities - who can easily earn six-figure deals for one-year endorsement contracts - underscores the steep challenge that Washington faces in policing this growing offshore industry.

The overseas casinos, which allow people to play poker against other gamblers, engage in table games like blackjack and bet on sports, are legal and licensed in dozens of jurisdictions around the world. In Britain, a handful of casinos are listed on public stock exchanges.

Revenue from Internet gambling is projected to reach almost $12 billion this year, up from $8.3 billion in 2004, according to Sebastian Sinclair, a gambling industry analyst with Christiansen Capital Advisors. Americans account for more than half of the amount wagered, Internet casino executives and industry analysts say.

The popularity has soared in recent years with the boom in poker, particularly Texas Hold 'Em, and its increasing prominence on cable television.

Still, the industry insists that online gambling would be much larger were it not for efforts by federal prosecutors and some financial institutions.

Over the past five years, many American banks that issue credit cards have apparently slowed the industry's growth by refusing to accept transactions processed by Internet casinos. Americans participating in the betting have turned to online payment services that allow them to place bets with money put into escrow accounts.

Last year, faced with an investigation by a federal prosecutor in St. Louis, Missouri, several big-name media companies, including Clear Channel and Infinity Broadcasting radio, stopped accepting advertisements for offshore casinos. The Internet search sites Yahoo and Google later made the same decision.

But ads for online gambling sites are still widely available in magazines and on radio and cable television channels, including the ESPN sports TV network. And some ads have returned to Clear Channel stations.

In 2004, the U.S. attorney's office for the Eastern District of Missouri vowed to pursue sports gambling sites, "as well as the promoters, aiders, and abettors of such criminal enterprises." Lawyers representing Internet gambling operations, however, said it appeared that the investigation had stopped, or at least slowed considerably.

Jaclyn Lesch, a spokesman for the Justice Department, declined to comment, saying the investigation was continuing.

In any event, the marketing of online casinos and sports betting sites is regaining momentum, said Will Griffiths, the director of marketing for Betonsports.com, a casino based in Costa Rica and listed on the London Stock Exchange.

Griffiths said that in some cases the broadcasts have been carefully worded to avoid provoking the Justice Department.

For instance, a radio campaign that began in October on some Clear Channel stations repeatedly mentions "Bet on Sports" as a great source for betting information and includes a telephone number where people can get information rather than the address for an Internet site.

Another tactic used by media companies to circumvent the threat of prosecution is to allow advertising of Web sites operated by offshore casinos that let people play various table and poker games with no money. The free sites then direct people to their gambling operations.

Legal specialists said any celebrities targeted by prosecutors could defend themselves by arguing that they were not aware that the enterprises they were promoting were illegal. The sites continue to seek new celebrities to market their products. This month, Robert Iler, a young actor who plays Tony Soprano's son on the HBO television series "The Sopranos," started appearing on betcris.com, a Costa Rica-based sports betting site and casino.

The company sought out Iler, according to its chief executive, Mickey Richardson, after he was caught in a police raid on an illegal card game in New York.

"When we heard the news, we decided to get into contact," Richardson said, as a way of drawing attention to the company's claim that playing poker online "is the safe thing to do."

Richardson said that the interest in online gambling among Americans has picked up again in recent months as the marketing has been stepped up.

The federal government "probably has got its hands full with other things right now," he said. Besides, he added, online gambling "is probably a train that can't be stopped."