LAS VEGAS — Sheldon Adelson, the billionaire casino executive keeping Newt Gingrich’s presidential hopes alive, has relayed assurances to Mitt Romney that he will provide even more generous support to his candidacy if he becomes the Republican nominee, several associates said in interviews here.

The signals from Mr. Adelson, whose politics are shaped in large part by his support for Israel, reflect what the associates said was his deep investment in defeating President Obama and his willingness to play a more prominent role in the Republican Party and conservative causes.

The assurances have been conveyed in response to a highly delicate campaign by Mr. Romney and his top Jewish financial supporters to dissuade Mr. Adelson from adding to the $10 million that he and his wife have given to a pro-Gingrich “super PAC,” Winning Our Future, that has been tearing into Mr. Romney through television advertising.

Several people who have spoken with Mr. Adelson over the past two weeks said he would most likely continue to help the group as long as Mr. Gingrich remained in the race. But, they said, he is concerned that additional deep-pocketed donors have not joined him. And, they said, his affection for and loyalty to Mr. Gingrich, who met with him here on Friday, have not blinded him to the reality that the nominating contest is tilting in Mr. Romney’s favor.