RICHMOND, Va. (AP) — Republican presidential nominee Mitt Romney on Friday accused the vice president of "doubling down on denial" over the deadly invasion at the U.S. Consulate in Libya, leaving the White House to defend its handling of the attack that killed its ambassador and three other Americans.

Biden said in a debate Thursday night that "we weren't told" there had been requests for more security at the U.S. Consulate in Benghazi ahead of the terrorist attack one month ago.

A State Department official testified before Congress on Wednesday that she had, in fact, refused requests for more security in Benghazi because the department wanted to train Libyans for the task. Another U.S. official testified he had argued unsuccessfully for more security for weeks.