Mayor Bloomberg is throwing a party to welcome Senator Clinton back from the presidential campaign trail, but the billionaire said he has no plans to help with her campaign debt.

The fete this evening at Gracie Mansion, where Big Apple martinis and barbecue are on the menu, is not a fundraiser for Mrs. Clinton, who’s still working to retire millions of dollars in debt from the hard-fought Democratic primary that she lost to Illinois Senator Obama.

Mr. Bloomberg said he’s hosting the reception simply to honor her and welcome her back from the 18-month-long fight.

“As you know, she worked her heart and soul out on the presidential campaign,” Mr. Bloomberg said before the party. “It didn’t turn out the way she would have liked, and lots of other people would have liked, but now she’s back being a full-time senator, and I thought it’s just a nice ways to say thank you to her.”

The mayor, who paid for the party himself, added that he had no plans to help with her debt.

Organizers expected more than 400 guests at the celebration, which was to be held at the official mayoral residence; Mr. Bloomberg lives at his own town house and uses the official mansion for ceremonial events.

The menu included hot dogs, burgers, and chicken on the grill, with mini cupcakes and ice cream sundae stations.

The Broadway cast of “Hair” was set to perform a number from the show, and actor Chevy Chase was also part of the evening’s entertainment. Organizers did not give a reason why those entertainers were chosen.

Mr. Bloomberg did not host a party for his Republican predecessor, Mayor Giuliani, another New Yorker who ran for president this year.

Mr. Bloomberg and Mrs. Clinton have a complicated history: While they always exchange warm words publicly, Mr. Bloomberg never quite got over the fact that Mrs. Clinton did not cross party lines and endorse him for re-election in 2005, when he was still a Republican and was running against a Democrat whose mayoral bid was a long shot.

And he did not endorse her or anyone in the primary. Thus far he has not said whom he’ll support in the general election.

For much of the Democratic presidential primary race, Mr. Bloomberg also was considering mounting his own independent presidential bid. During those months, he expressed measured praise for Mrs. Clinton, calling her a good senator who has been there whenever he needed her.

Mrs. Clinton has been more reserved about Mr. Bloomberg over the years. She occasionally commends him for advocating the city’s interests in the causes they share, such as fighting for homeland security money and aid for sick ground zero workers.