SOMERSET, Pa. -- U.S. Sen. Arlen Specter and Pennsylvania Gov. Ed Rendell signed a letter of commitment Friday to build a memorial for victims of the 9/11 terrorist hijacking of United Airlines Flight 93.

"There has never been a more heroic act than that which occurred on Sept. 11th, 2001," Specter said at a news conference at the Somerset Trust building in Somerset.

Video:Flight 93 Memorial Promised By 9/11/11

A temporary memorial to the 40 victims was established shortly after the crash at the site, which is in a large field just north of Shanksville.

Rendell said he feels the families' frustrations at the lack of progress on a permanent memorial.

"We have cleared all the road blocks. We will have this memorial ready and available for people to visit no later than Sept. 11, 2011," Rendell said. "Everyone's committed to the concept of having a memorial that in 50 years hence, people could come from all over the world to hear that story and what those 40 brave people did on that day."

Groundbreaking is scheduled for this fall, now that property acquisitions are nearly complete.

"That to me is the key piece of making sure by the 10th anniversary, that we will have a substation memorial to dedicate," said Patrick White, whose cousin, Louis "Joey" Nacke II, was aboard Flight 93.

Rendell also said the state will immediately pursue the design and construction of an access road off of Route 30 to the memorial site. He's requesting the Legislature approve a special capitol budget bill to pay for it.

On May 2, the committee will unveil final plans for "the sacred ground." Right now it's designed as a lake surrounded by trees, benches and panels with the names of the Flight 93 victims.

The permanent memorial is expected to cost about $57 million. About $30 million is to be covered in private donations, the rest from federal and state funds.