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House Speaker John Boehner is facing mounting pressure to create a special or select committee to investigate the Benghazi terror attacks in which four Americans were killed.

The House resolution to form a special committee now has at least 139 co-sponsors who are putting Boehner in the difficult position of leading efforts to get the White House to release emails on Benghazi-gate but not agreeing to the demands of many rank-and-file Republicans.

The resolution is sponsored by Virginia Rep. Frank Wolf who suggested to Boehner in a forceful, four-page letter Thursday that the Obama administration perhaps failed to adequately prevent the deaths of the Americans killed and injured in the Sept. 11, 2012, attacks on the U.S. outpost in Benghazi, Libya, and that not appointing the committee could make the Republican-led House “complicit in that failure.”

An ABC News story said the CIA’s explanation of the Benghazi events changed 12 different times before being made public.

Susan Rice, the U.S. ambassador to the United Nations, said five days after the attacks, while making the rounds on the Sunday talk shows, that the strikes appeared to be “spontaneous” and sparked by protests elsewhere in the Middle East about an anti-Islamic video.

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    However, references to “Islamic militants” and terror attacks in the original CIA reports were scrubbed from Rice’s final talk points.

    Wolf said that after the ABC News report the number of co-sponsors increased to 144, about 60 percent of the House Republican Caucus.

    The pressure to form such a committee also increased after three career State Department employees and self-proclaimed “whistle blowers” testified Wednesday about Benghazi before the House Committee on Oversight and Government Affairs.

    Wolf argues a select committee is needed to strengthen subpoena powers and so one chairman or director can bring together the expertise of the different standing committees.

    “If you don’t use the subpoena power, people will not come in and testify, because if you’re 50 years old and you’re a federal employee, you have two kids, maybe two college tuitions, you have a mortgage on your house in Arlington County, you’re not going to risk your career,” Wolf told conservative talk radio host Hugh Hewitt on Friday.

    He also said somebody from the Armed Services Committee should be included on the panel because the Defense Department is involved in the Benghazi matter. And the Intelligence Committee should be included because the CIA and the office of the Director of National Intelligence are also involved.

    Boehner on Thursday again declined to commit to appointing a committee, saying he has “confidence” in the committees already holding investigations.

    Such committees have been appointed to investigate Watergate and the Sept. 11, 2001, terror attacks.

    Beyond the issue of whether State Department officials and White House deputies changed the CIA memo for political reasons, in the height of Obama’s re-election effort, are issues of whether the U.S. provided adequate security at the compound and made full attempts to repel the attacks and rescue Americans.

    Republican Sens. John McCain, Arizona, and Lindsey Graham, South Carolina, renewed their call after the Wednesday hearing for a select committee.

    Graham, who with McCain had led Senate Republican efforts to get to the bottom of the Benghazi issue, told The Hill that he has urged Boehner to create the committee.

    “I've raised it to him, I've talked to him,” he told the newspaper. “It's his decision to make, but we're making a big mistake by not doing a select committee.”