GOP presidential candidates are wrong to challenge President Obama’s citizenship and deserve to lose in 2012 if they keep it up, Mayor Bloomberg said yesterday.

Instead, Republicans should focus on the deficit, unemployment and immigration, Bloomberg said. “If the Republican Party doesn’t start addressing that, they will lose and they deserve to,” the mayor said on “Fox News Sunday.”

He declined to take a dig at “birther”-in-chief Donald Trump, calling the mogul a “friend” and a “New York icon.”