WASHINGTON – A special U.S. House committee looking into the deadly Benghazi, Libya, attacks in 2012 will interview a host of current and former high-ranking Obama administration officials as it speeds the pace of the investigation.

The panel’s Republican chairman Rep. Trey Gowdy has previously said he will ask Hillary Rodham Clinton, secretary of state at the time of the attacks, to testify at a public hearing before the 12-member committee. He said Friday that appearance should occur “as soon as possible.” Clinton is widely expected to run for president in 2016.

Other high-ranking officials he said he intends to interview include former Defence Secretary Leon Panetta and former CIA director David Petraeus, as well as White House chief of staff Denis McDonough and national security adviser Susan Rice.

Gowdy also said he wants to interview Cheryl Mills, a longtime Clinton aide who was her chief of staff when the attacks occurred at the U.S. diplomatic outpost in Benghazi, killing Ambassador Chris Stephens and three other Americans.

The lawmaker said last week he was frustrated at the slow pace of the investigation and was going to “ratchet it up.” Dem,ocrats maintain the investigation is politically motivated and aimed at damaging Clinton’s presidential prospects.

Gowdy said Friday that the interviews with the high-ranking officials will begin as soon as April, after the panel interviews 22 potential witnesses who work for the State Department or have knowledge of the attacks.

He called the timeline for new interviews “ambitious” but said he intends to “stay with this schedule and will issue subpoenas if necessary.”

Clinton spokesman Nick Merrill said Friday that a reporter “should check in with” Democrats on the Benghazi panel for a response to Gowdy’s letter

Gowdy also plans to interview former UN Ambassador Thomas Pickering and Adm. Mike Mullen, who chaired an independent panel that reviewed the September 2012 attacks.Pickering was President George H.W. Bush’s U.N. envoy, and Mullen was the top U.S. general under Presidents George W. Bush and Barack Obama.

Their report harshly criticized the State Department for its security posture in the months before militants stormed the Benghazi facility. But House Republican members said their review was incomplete and lacked independence.

Rep. Elijah Cummings, the top Democrat on the Benghazi panel, said it was not clear what additional questions Gowdy and committee Republicans want to answer.

A majority of the 20 people named as likely witnesses “have already provided information to Congress through prior interviews and testimony – in some cases multiple times – during seven previous congressional investigations,” Cummings said.

Committee Democrats sent a letter to the House Administration Committee this week expressing concern over what they called a secretive, unlimited budget for the select committee.

The panel spent nearly $1.8 million last year and is on pace to spend more than $3 million this year, Democrats said. That total is more than several House committees with legislative and oversight jurisdictions and is larger than the amount House Republicans allocated to investigate Hurricane Katrina in 2005, Democrats said.

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