SAN FRANCISCO — The federal crackdown on online gambling has tied up the funds of thousands of U.S. patrons of two of the largest services.

The crackdown on BetOnSports, which no longer takes sports wagers from the United States, and Neteller, an Internet payment service popular among gamblers, is intended to put a dent in the $10.6 billion industry.

And it has: Following federal charges against executives from both companies, dozens of the more than 2,300 Web sites that service online gambling have stopped taking U.S. wagers.

Still, the actions against Bet-OnSports and Neteller have left the online accounts of their U.S. customers frozen until legal issues are resolved.

"The truth is that the money is in limbo and the companies are not required to refund any money until a successful prosecution or settlement takes place," says Michael Tew, principal of gaming consultant CapitalHQ. "This could take years." Funds from other gambling sites are not tied up, Tew and others say.

Most U.S. customers of Bet-OnSports have been waiting to cash out money in their accounts since July, when a federal grand jury issued a 22-count indictment charging CEO David Carruthers with racketeering, conspiracy and fraud. BetOnSports handled $1.77 billion in bets during its 2005 fiscal year, with more than 90 percent of wagers from the United States. An attorney representing the company declined to comment.

Neteller founders Stephen Lawrence and John Lefebvre were arrested in January on a charge of conspiracy to transfer funds with the intent to promote illegal gambling.

Though money-transfer companies such as Neteller do business with financial institutions and merchants, many also allow gambling companies to transfer money collected from U.S. gamblers to bank accounts outside the United States. Neteller last month closed its U.S. Internet gambling services, erasing about two-thirds of its business.

Neteller offers few instructions for customers trying to cash out their accounts. "We are working to resolve all withdrawal issues, but in the meantime we continue to maintain these funds in trust on your behalf," says a posting on the company's Web site.

Neteller declined to comment. The company processed more than $7 billion in online gambling transactions in its 2005 fiscal year. FBI Agent Neil Donovan says funds from Neteller are being held in court as potential evidence. Some customers may get their money back, but he did not provide a timetable.

A law signed by President Bush in October bans the use of credit cards, checks and electronic fund transfers for Internet gaming. U.S. residents place more than half of all bets to major offshore casinos.

BetOnSports has settled civil charges with the Justice Department but not criminal charges. Carruthers' case is separate.