Mayor Bloomberg will be in attendance when the NBA resumes with a Christmas Day tipoff at Madison Square Garden — but don’t assume he’ll be rooting for the Knickerbockers.  Check where Bloomberg’s loyalties lie after the jump.

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Then again, the Boston-bred billionaire mayor probably won’t be wearing a Larry Bird jersey to the much-anticipated tilt between the Knicks and the Boston Celtics.

“I grew up in Boston so I was a big Celtics fan,” Bloomberg said, being cagey in a convo on his weekly radio show about his allegiance in the hoops-is-back tilt. “And the first game this year is at Madison Square Garden — it’s the Knicks versus the Celtics.”

“So I am going to have to be very careful to not smile no matter who makes a basket,” Bloomberg joked to WOR host John Gambling.

But Bloomberg has recently been more open about his basketball rooting interests. He appeared on the ABC talk show “The Chew” in October and admitted that his affection for the Knicks is trumped whenever they play the NBA’s most storied franchise.

“I came from Boston [and\] everybody accuses me of being a Red Sox fan, but I never was,” he said at the time. “I was a Celtics fan, much to the Knicks’ annoyance.”

“But even now I root for the Knicks, unless the Celtics are in town.”

Bloomberg, who sat courtside at MSG when the two teams met in last season’s playoffs, has never claimed to be much of a sports fan, but several people who work in City Hall have said the mayor genuinely — if quietly — roots for the Celtics.

When running for office in 2001, Bloomberg bobbled a question about whether he liked the Yankees or the Mets by simply answering “I grew up in Boston” and then smiling.

Since then, he has loudly declared his affection for the New York baseball teams, often wearing their logos while attending games

– even sporting a jacket with the blue-and-white interlocking NY on it when the Yanks play the Red Sox — almost unheard of behavior for a son of Boston.

Of course, New York politicians have a long tradition of waffling on their sports allegiances when the time comes to go hunting for votes.

Hillary Clinton, who grew up a Chicago Cubs fan, suddenly announced that she rooted for the Yankees while running for Senate.

And even Rudy Giuliani, perhaps the city’s most famous Yankees fan, announced he was rooting for the Red Sox in the 2007 World Series — no doubt because he was then campaigning in New Hampshire during his flameout White House bid.

NYDN