De Niro said in a statement that he was speaking "with satirical jest" at the event Monday night in New York. The actor says his remarks "were not meant to offend or embarrass anyone - especially the first lady."
The joke drew a complaint from Newt Gingrich, who said the racial reference to the Republican candidates' wives was "inexcusable" and demanded an apology from President Barack Obama.
The White House referred questions to Obama's re-election campaign. Mrs. Obama's campaign spokeswoman Olivia Alair called the joke "inappropriate" but declined further comment.
