WASHINGTON -- Former GOP presidential candidate Rick Santorum said he was not interested in serving in Mitt Romney's administration, should the former Massachusetts governor beat President Barack Obama in November.

"I want to help Mitt Romney get elected president, and I'll be happy to help and advise him if he wants my advice as president, but my objective right now is to serve my family and provide for them," Santorum said Sunday morning on CNN's "State of the Union."

When host Candy Crowley asked him if that was a "flat no," Santorum replied, "Yeah, it is pretty much a flat no," adding that his response didn't reflect a desire not to help Romney.

Crowley brought up some the criticisms Santorum leveled at Romney while they were both vying for the GOP nomination, pointing out that he had questioned Romney's authenticity and convictions.

"When you talk about this race to your children and grandchildren, is there anything you say, 'I went too far here and I wish I had not done that?'"

Santorum responded by addressing comments he made about Obama, pointing out that he has said he believed he went too far in calling the president a "snob."

When pressed specifically about his comments about Romney, Santorum said, "Well, I have no problem questioning authenticity, and those are all things that I thought were legitimate differences between us as candidates, and the same thing with President Obama. I mean, there are differences between us. I don't back away from any of those things, but at the same time, clearly the difference between President Obama and Mitt Romney is a chasm, and I have a great degree of comfort supporting Gov. Romney as the choice between the two."

While Santorum has endorsed Romney, his support has been less than enthusiastic. His official backing came late on a Monday night in May, in the 13th paragraph of an email to supporters. He gave his endorsement only after securing an hourlong meeting with Romney in Pittsburgh, and the two have yet to appear together in public.