LAS VEGAS -- A group of 128 gamblers plunked down $25,000 each on Tuesday to compete in the first tournament of this year's World Series of Poker, generating the largest ever pool for a heads-up no-limit Texas Hold `em tournament and giving the series an encouraging sign amid a state of weakness for online poker in the United States.

The field -- made up of popular poker professionals known for gambling at high limits -- began competing for a piece of a $3 million prize pool, with the winner getting more than $851,000.

"Been going to WSOP for over 10 years and am giddy as ever, if not more," four-time gold bracelet winner Daniel Negreanu said on Twitter before entering the tournament. "WSOP is very special, and I can't wait to get started on the grind."

Negreanu was eliminated in the first round.

With casino officials optimistic yet admittedly unclear exactly how the World Series of Poker would be affected, two of 58 tournaments began with the promise of awarding millions in prize money, gold bracelets and instant fame to winners in many poker variations.

The series culminates in July with the $10,000 buy-in no-limit Texas Hold `em main event, and then a nearly two-week affair that ends in November after a break to give its top nine players several months to think about how to finish their run. Last year's winner, Canadian professional Jonathan Duhamel, won $8.9 million after topping a field of 7,319 players.

This year's set of tournaments will play out against a backdrop of legal problems for online poker companies that aren't affiliated with the series, but have contributed to making poker grow into an international industry worth billions, helping the series attract plenty of entrants and fans.

Online play in the United States has largely stopped since mid-April, when federal authorities in New York indicted 11 people tied to PokerStars, Full Tilt Poker and Absolute Poker on charges they tricked banks into illegally processing payments for gambling. Three more people and a handful of smaller websites were targeted this month through a separate federal case in Maryland, including a site that once promoted itself through card playing icon Doyle Brunson.

The indictment left millions in player deposits in limbo, with many worried they wouldn't be able to access their bankrolls in time for the tournaments.

Series spokesman Seth Palansky said the numbers for the series' first day were encouraging.

"We've always been optimistic," he said. "We're thrilled with the start. It's early, but we're very encouraged by what today tells us for the rest of the WSOP."

A casino employees-only event that cost $500 to enter attracted 850 players, up nearly 18 percent compared with the same tournament last year. The winner of that two-day event will win more than $82,000.

The series upped the buy-in for its heads-up title tournament to $25,000 from $10,000 last year, generating a bigger prize pool to be split between 16 players, fewer than last year.

As the tournament started, players crowded a section of a tournament room at the Rio All-Suite Hotel & Casino to watch the bracket-style matchups get randomly chosen by a computer.

Competitors include Duhamel, eight-time gold bracelet winner Erik Seidel and Daniel "jungleman12" Cates, a 21-year-old online sensation making his debut at the series.

"I think the fields will be slightly tougher," Cates said of how the series might be affected by the online poker indictments.

Cates, who said the indictments made him more discerning about how he gambles because he has less available cash, said fewer smaller tournaments giving entry fees as prizes mean players need the skill -- and cash -- to buy themselves in.

The conditions have not been seen in the poker world since it began riding booming growth in 2003, when then-unknown amateur Chris Moneymaker won $2.5 million in a transcendent moment for the sport. The growth spawned millions of fans and players who fueled an international online poker industry that grew to as much as $6 billion in the United States and even more overseas.

A 2006 law made online poker technically illegal in the United States, but operators -- believing the law didn't properly define illegal gambling and saying poker is more skill than luck -- kept games and money flowing. The U.S. Justice Department disapproved.

For years, the popular sites sent players to the series through smaller tournaments that awarded cash for entry fees. The series, owned by casino giant Caesars Entertainment Corp., hasn't tracked this since 2007, when it stopped letting third parties directly buy entries for players.

"There'll probably be a lot of chatter," said Phil Hellmuth, an 11-time bracelet winner who has won $6.2 million at the series since 1988. "It's still the purest poker festival on the planet."

Hellmuth said that despite critics who think the series may have a down year, he thinks the tournaments and cash games at the Rio All-Suite Hotel & Casino will grow because good players quickly lend each other money, and the series is the poker world's central event each year.

And he thinks that players have studied and will come with more knowledge about the game than ever before.

"Last year, the 2010 World Series of Poker, I really played some good poker and it's aggravating because the results didn't show it," he said. "One of these years, I'm going to put together playing great and running great, and that's when you win a couple bracelets."

In the first round, Cates faced French professional Bertrand Grospellier, who placed 12th in the head-up tournament last year and has won nearly $248,000 since 2006.

Cates said he didn't know if he'd win a bracelet this year, but he hoped to try.

"My only real expectation is to make some sort of profit," Cates said. "One of my goals is to have as much success live as I've had online."