NORTH HUNTINGDON, Pennsylvania (Reuters) - Republican Mitt Romney's campaign unleashed new attacks on President Barack Obama on Tuesday, with one of Romney's surrogates saying he wished Obama "would learn to be an American" before apologizing within hours for the remark.
On a conference call with reporters, former New Hampshire Governor John Sununu blasted Obama and his campaign, calling them a "bunch of liars."
"I wish the president would learn how to be an American," Sununu said, although he backed away from that comment.
Obama has repeatedly sought to end false speculation by many conservatives that he was not born in the United States and thus is not legally able to serve as president.
Romney has repeatedly tried to avoid the so-called birth issue, and Sununu was quick to retreat from his statement.
"What I thought I said but what I didn't say is the president has to learn the American formula for creating business," Sununu said.
He later apologized in a CNN interview, saying: "Frankly, I made a mistake. I shouldn't have used those words."
The conference call appeared to be a new attempt at a counterpunch from the Romney campaign after days of damaging assaults on career at private equity company Bain Capital and his refusal to publicly disclose more than two years of his tax returns.
Obama campaign spokeswoman Lis Smith said Romney's team was trying to deflect attention.
"The Romney campaign has officially gone off the deep end. The question is what else they'll pull to avoid answering serious questions about Romney's tenure at Bain Capital and investments in foreign tax havens and offshore accounts," she said in a statement.
"This meltdown and over-the-top rhetoric won't make things better. It only calls attention to how desperate they are to change the conversation."
(Editing By Alistair Bell and Christopher Wilson)