A special US House committee investigating the deadly 2012 attacks in Benghazi, Libya, began in May with promises of bipartisanship and cooperation. Eight months later, the panel has degenerated into finger-pointing and accusations of political grandstanding and power plays.

As the panel holds its third public hearing on Tuesday, Democrats complain that the panel's Republican chairman has excluded them from crucial steps in the investigation, while Republicans say Democrats are playing politics.

In a strongly worded letter, Representative Elijah Cummings of Maryland, the panel's top Democrat, said the panel's chairman, Republican Representative Trey Gowdy, has used different standards for Republicans and Democrats and has held secret meetings with witnesses from the State Department and other agencies.

"Perhaps most importantly," Cummings wrote in a letter last week, Gowdy has "withheld or downplayed information when it undermines the allegations we are investigating." The Associated Press obtained a copy of the letter and two others sent by Democrats to Gowdy.

Gowdy said in response late on Monday that he has the authority to unilaterally subpoena witnesses, but he promised to give Democrats a week's notice before issuing such a subpoena.

"Bipartisanship is a two-way street," Gowdy said in a letter to Cummings. "I have known you to be a fair partner and expect for that cooperation to continue."

Committee spokesman Jamal Ware was less diplomatic. He said Gowdy was disappointed that Democrats had released "correspondence that attempts to politically characterize sources' private discussions with the committee".

As chairman, Gowdy "has operated the Benghazi Committee in a more-than-fair and fact-based manner", Ware said, adding that Gowdy will continue to address any legitimate Democratic concerns. "He will not, however, allow the committee's investigation to be hamstrung by politics."

Such an outcome appeared increasingly unlikely, as the bipartisan tone set in May, when the 12-member committee was created, appeared to dissipate

Gowdy has said he will pursue the facts of the Sept. 11, 2012, attack on a US post in eastern Libya that killed Chris Stevens, the US ambassador, and three other US citizens.

Gowdy's approach has drawn criticism from some conservatives, who accuse him of failing to stand up to what they see as resistance from the Obama administration to produce documents and witnesses related to the events in Benghazi, a topic that has been the subject of numerous congressional investigations.

A report by the House Intelligence Committee report in fall found that the CIA and the military acted properly in responding to the 2012 attacks. The panel determined there was no intelligence failure, no delay in sending a CIA rescue team and no missed opportunity for a military rescue.

Xinhua - AP