WASHINGTON - A House committee chairman vowed yesterday to seek additional testimony on the administration's handling of last year's deadly attack on the U.S. diplomatic post in Libya as another prominent Republican lawmaker called for a special committee to investigate.

WASHINGTON — A House committee chairman vowed yesterday to seek additional testimony on the administration’s handling of last year’s deadly attack on the U.S. diplomatic post in Libya as another prominent Republican lawmaker called for a special committee to investigate.

The dispute over last September’s assault in Benghazi that killed four Americans dominated the network talk shows. Leaders of both parties debated whether the administration paid enough attention to security before the attack, did enough to respond once violence began and tried to deceive the public afterward in the midst of an election campaign.

“I’d call it a cover-up,” Sen. John McCain, R-Ariz., said on This Week on ABC News. “I would call it a cover-up in the extent that there was willful removal of information, which was obvious.”

McCain called for a select committee to investigate, saying that “there are so many questions that are unanswered.” Last week, several House Republicans called for a special investigation in that chamber as well.

Rep. Darrell Issa, R-Calif. and chairman of a House Oversight and Government Reform Committee investigating the episode, also referred to a cover-up as he charged that the administration scrubbed talking points to falsely blame an incendiary anti-Muslim video rather than specific terrorist groups.

“The American people were effectively lied to for a period of about a month,” he said on Meet the Press on NBC News. “They were in fact covering up an easy attack that succeeded, that was from the get-go really about a terrorist attack. It was never about a video.”

Issa said he would deliver requests for testimony today to former Ambassador Thomas Pickering and Adm. Mike Mullen, the retired chairman of the Joint Chiefs of Staff, who led a State Department review of the incident that critics considered inadequate.

Issa, whose committee has been leading the latest investigation in the House, said he did not believe a special investigation would be necessary.

Ambassador Christopher Stevens and three other U.S. government employees were killed when the Benghazi diplomatic compound was stormed on Sept. 11. The highly charged and politically polarized debate about the episode flared up last week with congressional hearings featuring State Department officials who questioned the handling of the situation, including the failure to make any effort to intervene militarily.

Criticism was further fueled by the disclosure of drafts and email messages showing how the administration directed the editing of talking points after the attack to remove references to al-Qaida and another terrorist group, and any warnings of threats in Benghazi. The White House last week said it was trying to avoid speculation and stick to what was definitively known at the time.

Democratic lawmakers and a former Pentagon chief came to the defense of the administration yesterday.

Former Defense Secretary Robert M. Gates, who served several Republican presidents in various capacities, before staying on under President Barack Obama for 2 1/2 years, rebutted the suggestion that the Pentagon could have scrambled jets or special forces during the attack a “cartoonish impression of military capabilities.”

“Given the number of surface-to-air missiles that have disappeared from (Moammar) Gadhafi’s arsenals, I would not have approved sending an aircraft, a single aircraft over Benghazi under those circumstances,” he said on Face the Nation on CBS News.

Democratic Sen. Richard J. Durbin of Illinois, the Democratic whip, accused the Republicans of partisan persecution.

“Unfortunately, this has been caught up in the 2016 presidential campaign — this effort to go after Hillary Clinton,” he said. “She didn’t have any direct-line responsibility for the decisions that were made, but they want to bring her in because they think it’s a good political show, and I think that’s unfortunate.”

Issa made clear he was not yet satisfied and planned to pursue the matter by seeking the private testimony from Pickering and Mullen.

“Ambassador Pickering, his people and he refused to come before our committee,” Issa said.

Pickering, sitting next to him on the Meet the Press television set, interrupted. “That is not true,” he said.

“We have it in writing,” Issa countered, suggesting perhaps it was the White House that refused to let him appear.

“I said the day before the hearings I was willing to appear, to come to the very hearings he excluded me from,” Pickering said.

Issa said he wanted to explore whether the Accountability Review Board led by Pickering and Mullen interviewed all possible witnesses and focused high enough in assigning responsibility. “ Ultimately, if that got it right, then we can put this to a rest,” he said. “We believe it was insufficient.”

Pickering appeared on several shows to defend the panel’s actions. Under questioning on CBS, he said his panel had the opportunity to interview Clinton, then secretary of state, but did not ask any questions because they believed they had already established the facts and level of responsibility.

“We didn’t believe that was necessary, and I don’t see any reason to do so now,” he said.