By Steve Holland
RICHMOND, Virginia (Reuters) - Mitt Romney accused Vice President Joe Biden on Friday of contradicting the testimony of U.S. State Department officials on Libya, in an escalation of the Republican presidential challenger's attacks over the September 11 deaths of four Americans there.
Hoping to puncture President Barack Obama's credibility on foreign policy ahead of the November 6 election, Romney jumped on comments that Biden made on Thursday night during a debate with Romney's vice presidential running mate, Paul Ryan.
When asked whether the U.S. diplomatic compound in Benghazi, Libya had asked for more security ahead of the attack, Biden said: "Well, we weren't told they wanted more security again. We did not know they wanted more security again."
Two State Department officials gave sworn testimony on Wednesday at a congressional hearing in Washington saying they had repeatedly requested beefed-up security for the compound before U.S. Ambassador Christopher Stevens and three other Americans were killed in the assault at the site on September 11.
"The vice president directly contradicted the sworn testimony of State Department officials," Romney told a campaign rally in Richmond. "He's doubling down on denial."
"When the vice president of the United States directly contradicts the testimony, the sworn testimony of State Department officials, American citizens have a right to find out what's going on," he said.
Romney's campaign is focused on the weak U.S. economy but increasingly he has turned his attention to foreign policy, long considered a strength for Obama because he ordered the mission that killed al Qaeda leader Osama bin Laden and is bringing home U.S. troops from unpopular wars in Iraq and Afghanistan.
Romney, whose solid debate performance against Obama on October 3 halted a slide in the polls and gave him momentum, argues that Obama has projected a weak foreign policy in many ways by alienating allies and not being tough enough over Iran's nuclear ambitions.
Romney has been demanding answers from Obama over the American deaths in Libya. "We're going to find out. And this is a time for us to make sure we do find out," he said.
The former governor of Massachusetts has not always been sure-footed on foreign policy. His initial reaction to the violence in Libya as well as in Egypt was seen as an off-key attempt to politicize a national tragedy, and he drew sharp criticism from Democrats and some Republicans for it.
The comments on Libya during the vice presidential debate may prove to be simply a warm-up act to the next presidential debate, on October 16 at Hofstra University in New York, in which Obama and Romney will go head-to-head for a second time.
Romney's campaign has also sought to make an issue of what the Obama administration knew about what triggered the attack in Libya.
The White House initially said the violence was an impromptu reaction by Muslims upset at a video made in California that insulted the Prophet Mohammad. Days later, the administration publicly called it a terrorist attack on the 11th anniversary of the September 11, 2001, attacks.
"President Obama, this is an issue because Americans wonder why it was it took so long for you and your administration to admit that this was a terrorist attack," Romney told a rally in Asheville, North Carolina, on Thursday night before the debate.
(Editing by Alistair Bell; Editing by Will Dunham)