Aides say President Obama may have been smiling when comedienne Wanda Sykes blasted Rush Limbaugh at the White House Correspondents Dinner, Saturday, but he didn't think the joke was funny.

Press Secretary Robert Gibbs stopped just short of questioning Sykes' selection, saying, "I don't know how guests get booked. That's a White House Correspondents' Association thing."

Then he said "there are a lot of topics that are better left for serious reflection, rather than comedy. I think there's no doubt that 9/11 is part of that."

Sykes had condemned Limbaugh for saying he hopes the Obama administration fails.

She said to the audience, "to me, that's treason," and to President Obama she said, "you might want to look into this, sir, because I think Rush Limbaugh was the 20th 9/11 hijacker. He was just so strung out on Oxycontin he missed his flight."

Sykes knew she was treading on thin ice, asking after she told the joke, "too much?" She followed that by saying of Limbaugh, "I hope his kidneys fail, how about that?"

Wendell Goler serves as a senior White House and foreign affairs correspondent for Fox News Channel (FNC), joining the network in 1996.