Updated 8:24 p.m. ET, 5/6/2014
(CNN) - House Republicans have decided the select committee to investigate the Benghazi terror attack will include seven Republicans and five Democrats, according to two senior House GOP leadership aides.
The House is expected to vote on the legislation establishing the panel later this week.
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Earlier Tuesday, House Democratic Leader Nancy Pelosi demanded it be evenly split between Republicans and Democrats.
Now that the committee's structure has been decided, it's unclear whether Democrats will participate.
After a meeting among Democratic leaders, several sources in the room said their biggest concern is not about having fewer members, but having an equal say in how the panel will be run - especially regarding subpoena power.
Democrats said they plan to give Republicans a set of principles for how they would want the process to work, but privately don't expect them to go along with it. That would make it highly unlikely they would participate.
Rep. Jim Clyburn, a Democrat from South Carolina, told reporters he's "dead set" against members of his party participating in any panel that isn't modeled on the House Ethics Committee, which is evenly split.
Asked about concerns that Republicans would go unchallenged without Democrats on the committee, Clyburn said, "Let them drive it, they're driving it anyway - not bringing a noose to my hanging."
Rep. Steny Hoyer of Maryland, the No. 2 House Democrat, said "we did want it to be evenly split but we don't know the process that they are going to go through and we want to find that out."
Four Americans, including Ambassador Christopher Stevens, were killed in the September 2012 armed assault on the U.S. diplomatic compound in Benghazi, which is in eastern Libya.
House Speaker John Boehner said last week that he would form the select committee after Republicans said new information unearthed by a conservative watchdog group supported their claim that the Obama administration politicized its public response to the attack.
The White House said that development had nothing to do with Benghazi. Democrats have been sharply critical overall of the Republican-led investigation in the House.
Benghazi has become a partisan political flashpoint overall in Washington over President Barack Obama's conduct of foreign policy.