Mitt Romney said the attack on the US consulate in Libya is an issue in the presidential campaign because Americans wonder why it took the Obama administration so long to acknowledge it was a terrorist act.
He was responding to a charge by Barack Obama's campaign that the Republican ticket has been politicising the attack which killed the US ambassador to Libya and three other Americans.
At a rally in North Carolina, the Republican candidate read aloud comments from Obama spokeswoman Stephanie Cutter about the attack. "The entire reason that this has become the, you know, political topic it is, is because of Mitt Romney and Paul Ryan," Ms Cutter told CNN.
"No, President Obama," Mr Romney said. "It's an issue because this is the first time in 33 years that a United States ambassador has been assassinated. Mr President, this is an issue because we were attacked successfully by terrorists on the anniversary of September 11. 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."
In response, Obama campaign spokeswoman Lis Smith said Mr Romney was trying to "score cheap political points".
The back-and-forth came a day after Republicans used a politically charged House hearing to confront State Department officials about security at the US consulate in Libya and attack the Obama administration's early response to the Libya assault.
Ambassador Chris Stevens died in what administration officials now describe as an act of terrorism. In statements immediately after the attack, neither Mr Obama nor secretary of state Hillary Clinton mentioned terrorism, though Mr Obama referred to "acts of terror" in his Rose Garden statement the morning after the assault. Both Mr Obama and Mrs Clinton gave credence to the notion that the attack was related to protests about a privately made anti-Islam video.
"Some have sought to justify this vicious behaviour as a response to inflammatory material posted on the internet," Mrs Clinton said on the night of the attack. "The United States deplores any intentional effort to denigrate the religious beliefs of others. Our commitment to religious tolerance goes back to the very beginning of our nation. But let me be clear: There is never any justification for violent acts of this kind."
The day after the attacks, State Department officials described them in a conference call with reporters. They outlined a prolonged assault that involved attacks on two different buildings at the Benghazi consulate, with Mr Stevens and other officials trying to escape from one building only to be pinned down by gunfire in another.
Five days after the attack, UN ambassador Susan Rice said her best information at the time was that it stemmed from a protest that became violent. White House spokesman Jay Carney told reporters on Wednesday that in hindsight "there is no question that the security was not enough to prevent that tragedy from happening".