Two Senate Republicans are leading a charge in Washington to overturn a new Delaware law permitting betting on sports.

Sen. Orrin G. Hatch of Utah and Sen. Jon Kyl of Arizona wrote a letter earlier this week to Attorney General Eric H. Holder Jr. urging him to enforce a federal ban on sports betting in Delaware and New Jersey.

In the letter, first reported in the Washington Post, the lawmakers warn that "sports betting threatens the integrity of the pastimes our citizens enjoy and the nature of the games they follow" and ask Holder to "defend this statute in any pending litigation and to closely follow the events in Delaware to prevent any violations of federal law."

The letter comes as three racetrack casinos that offer slot-machine gambling in Delaware prepare to offer sports betting at their venues, starting early September at the start of the NFL season.

Delaware recently enacted legislation to permit sports gambling. The state is one of the four "grandfathered" to do so despite the federal prohibition in the Professional and Amateur Sports Protection Act. Congress passed the law in 1992 to cease the expansion of state- and tribal-sponsored sports gaming.

Dover Downs Hotel & Casino in Dover, the largest of the three Delaware casinos, is building a 7,500-square-foot sports book to offer single-game betting.

Meanwhile, New Jersey State Sen. Ray Lesniak (D., Union) filed a federal lawsuit in March against the Justice Department, seeking to overturn the ban on sports betting in other states.

Last month, Gov. Corzine, acknowledging the fierce competition that Atlantic City now faces, said he supported legalizing sports betting in his state.

Both Lesniak and Corzine say the state could make as much as $100 million taxing winnings alone. Lesniak envisions sports books at the Atlantic City casinos, as well as at the state's racetracks and off-track betting parlors.

The U.S. senators claim both Delaware and New Jersey "threaten to greatly expand sports gambling and undermine the integrity of our national pastimes."

Gaming analysts and other states, including Pennsylvania, are also closely watching.

"Delaware is in a very competitive environment," said Michael Pollock, managing director of Spectrum Gaming Group L.L.C. of Linwood, N.J. "Sports betting is one thing Delaware can provide that other states can't, so it's trying to leverage that edge, which is completely understandable."

But Pollock was less sure of the effort in New Jersey.

"This legislation that grandfathered Delaware has been in place since the early '90s, and I think that a number of states, including New Jersey, would like to see something happen to level that playing field, in terms of letting them provide sports betting," he said. "But I just don't see that happening anytime soon."