Las Vegas casino mogul Steve Wynn is urging Massachusetts lawmakers to make changes to the state’s gaming law, something they are reluctant to do for fear of reopening the debate about gambling.

Wynn flew into Boston nearly two weeks ago to talk to lawmakers about several sections of the law that concern him, particularly a provision requiring any gambler to pay state income tax on any winnings greater than $600 before leaving the casino.

The $600 cutoff is the lowest in the country and applies to all forms of gambling, including horse racing, table games at casinos, and slot machines. The Lottery already had a $600 cutoff. The cutoff was set low in the 2011 gaming law to make sure that gamblers didn’t walk off with their winnings and avoid paying taxes.

But concern is growing that the cutoff is so low that it could backfire on the state. Sources say Wynn has told lawmakers he is worried the low threshold could prompt many gamblers to cash out before they reach $600 in winnings or – even worse – skip Massachusetts altogether.

The low threshold also discourages certain types of bets. In horse racing, it’s possible to place three bets of $100, $200, and $200, for a total of $500, on one ticket. But if the $100 bet wins $700 and the two $200 bets don’t win anything, the state views the gambler as having $600 in winnings even though the bettor feels he wagered $500 and won only $200.

New Hampshire passed a similar $600 tax threshold in 2009. Losses mounted so quickly at the state’s horse tracks that the law was repealed in 2011.

Of 15 states that require gamblers to pay state taxes on wagering proceeds at the time they are won, Massachusetts has the lowest threshold at $600. Iowa is second at $1,000 and the rest use the same $5,000 threshold as the federal government. Only five states require withholding on slot machine winnings; the $600 threshold in Massachusetts is the lowest.

The Boston Herald reported this week that Wynn is pressing lawmakers for changes in the gaming law, but the tabloid had no information on what changes he wanted. That didn’t stop the Herald editorial page from telling Wynn to take a hike.

But there is growing support on Beacon Hill and at the Massachusetts Gaming Commission for revisiting the $600 threshold. An October memo by Jennifer Durenberger, director of racing at the Gaming Commission, suggested the threshold was having a negative impact on racing proceeds. She urged the commissioners to consider supporting legislation that would change the threshold.

On Beacon Hill, sources say, lawmakers are receptive to changing the threshold but wary of Wynn’s other concerns about the law, including the state’s periodic review of casino licenses and some of the provisions dealing with problem gamblers.

Lawmakers are nervous about amending the gaming law and reopening the gambling debate, but sources say the withholding threshold on winnings is technically located in a section of the general laws dealing with the income tax and could probably be revised without reopening the debate about gambling.