The US Treasury Department and Federal Reserve Board approved regulations on Wednesday designed to crack down on unlawful Internet gambling.
In a so-called "final rule," the US authorities outlined the regulations aimed at implementing an act passed by the US Congress in 2006 which seeks to prohibit illegal gambling on the Web.
The law bans US banks, credit card and financial companies from handling Internet gambling bets and has been the target of fierce criticism that it would be an enforcement nightmare.
It specifically prohibits gambling businesses from knowingly accepting payments made through credit cards, electronic funds transfers, and checks.
The Treasury Department said the final rule requires US financial firms that participate in designated payment systems to "establish and implement policies and procedures that are reasonably designed to prevent payments to gambling businesses in connection with unlawful Internet gambling."
Firms have until December 1, 2009 to be in compliance with the rule, the Treasury Department said in a statement.
The administration of President George W Bush has been accused of seeking to rush the regulations through before its term expires in January 20, 2009.
The law passed in 2006 was aimed at putting teeth into a de facto ban on US residents placing online wagers in locations such as Britain, Canada, Antigua and Gibraltar.
But the US ban on Internet gambling has been challenged as an unfair trade restriction at the World Trade Organization.