RICHMOND, Va. – Broadening his attack on administration foreign policy, Mitt Romney accused Vice President Joe Biden on Friday of "doubling down on denial" in a dispute over security at a diplomatic post in Libya that was overrun by terrorists who killed the U.S. ambassador and three other Americans.

"The vice president directly contradicted the sworn testimony of State Department officials," the Republican presidential candidate said, eager to stoke a controversy that has flared periodically since the attack on Sept. 11 "... American citizens have a right to know just what's going on. And we're going to find out."

President Barack Obama had no campaign appearances during the day, leaving it to White House press secretary Jay Carney to defend Biden's assertion in a campaign debate Thursday night that "we weren't told" of an official request for more security at the site.