Rep. Darrell Issa isn't backing down from his long-standing claim that the 2012 attack on a U.S. diplomatic post in Benghazi, Libya, was the work of al Qaeda terrorists, despite a new report by the New York Times that refutes that finding.

"What we do know is [the attack] is not an accident," Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, told NBC's "Meet the Press" on Sunday. "These are terrorist groups, some of them linked to or self-effacing or self-claimed as al Qaeda-linked."

The Obama administration has said the assaults were spontaneous and linked to protests earlier that day in Cairo against an American-made video denigrating Islam's prophet Muhammad. Issa, whose panel has been investigating the attacks that killed U.S. Ambassador Christopher Stevens and three other Americans, has led the GOP pushback against the White House's claim, saying evidence shows the attacks were planned in advance by an organized terrorist group.

The Times article published this weekend casts doubt on both positions.

"The reality in Benghazi was different, and murkier, than either of those story lines suggests," the Times reported. "Benghazi was not infiltrated by al Qaeda, but nonetheless contained grave local threats to American interests. The attack does not appear to have been meticulously planned, but neither was it spontaneous or without warning signs."

Issa, while not directly refuting the article, questioned the definition of "al Qaeda," arguing that since the terrorist group doesn't have a central command, militias inspired by the Islamic fundamentalist movement and its former leader, Osama bin Laden, should be considered part of al Qaeda.

"Look, it is not about al Qaeda as the only terrorist organization any more than Palestinian Islamic jihad or Hamas or Hezbollah," he said. "What I have claimed, and rightfully so, is Ambassador Stevens and others [were] alerted well in advance that they had a security threat.

"There is a group that was involved [in the attacks] that claims an affiliation with al Qaeda," he said.

Issa said he found no evidence to suggest the controversial anti-Islam video spurred the attack.

"The fact is people from this administration, career professionals, have said under oath there was no evidence of any kind of reaction to a video and, in fact, [that] this was a planned attack that came quickly," Issa said. "That's the evidence we have by people who work for the U.S. government and were under oath."

Rep. Joaquin Castro, D-Texas, a member of the House Foreign Affairs Committee, called Issa's position "a fairytale."

"I hope that Chairman Issa and others have learned a lesson from this," Castro said on the same program. "Some of the information that came out early [by the administration] -- although it may have been wrong -- that was their best effort. Darrell Issa and others took that and crusaded against the administration in a way that I think has been a big distraction for the American people."