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.