LAS VEGAS - Observers say the recently enacted U.S. law that bans gambling online could cut into the number of entrants to the planet’s richest card game — the World Series of Poker.

The number of players in the tournament, run by Harrah’s Entertainment Inc., has ballooned thanks largely to the online game. In 2003, a mere 839 participants took part when accountant Chris Moneymaker emerged from a $40 Internet tournament and went on to win the $2.5 million grand prize. This year, 8,773 players gambled for part of an $82.5 million prize pool and more than half are estimated to have won tournaments over the Web to play.

With the law banning banks from processing Internet gambling transfers set to be enforced before next year’s tournament, the well of poker players is expected to dry up.

“It’s going to affect the average player most dramatically. And those players are the ones that have kind of filled the ranks,” said Michael Bolcerek, president of the Poker Players Alliance, a 130,000-member group that fought the legislation.

“The hardcore ones will find somewhere, they won’t care whether it’s regulated,” said Bolcerek. “That’s what a prohibition does. It drives everything underground.”

Mike Sexton, who hosts the popular World Poker Tour on the Travel Channel, said the ban would hurt what has become considered a sport.

“I wouldn’t say it would put poker in a death spiral but in the long run it will hurt the growth of poker,” Sexton said. “The World Series of Poker is going to be devastated over this.”

Casino operators, however, were holding out hope.

“Poker’s enormous popularity won’t be changed,” said Alan Feldman, spokesman for MGM Mirage Inc.

The number of poker tables in Las Vegas has surged from 142 in 2003 to 405 in 2006, with many citing the growth to Internet players seeking to test their skills on the felt.

Slideshow   The Week in Sports Pictures A kayaker flips out, a racehorse eyes the Triple Crown and more. more photos

Organizers for the World Series of Poker, televised by Walt Disney Co.’s ESPN, also said they were not daunted by the new law. Before the legislation was enacted, ESPN, which has covered the tournament since 1993, signed on to cover it through 2010.

Tournament spokesman Gary Thompson said since 2005, organizers have not accepted third-party registrations for the $10,000 buy-in main event from online gambling companies with U.S. operations, and that hasn’t stopped it from attracting record fields.

“In 2005 and 2006 we had record fields each year. We’re confident again that 2007 will be the best one ever,” he said.

Thompson suggested that a loophole that allowed players who qualified online to pay their own entry fees directly, after being given the fees by online poker companies, would continue to pass muster with regulators.

PokerStars.com said it paid the way for 1,600 players who qualified online this year, while Bodog.com said it sent more than 500.

“We’re planning to accommodate a larger field than we ever had before,” Thompson said. “But whether or not we’ll have a larger field, nobody really knows.”