ALBANY – In an effort to accelerate construction at the World Trade Center site and to salvage a legacy that seems threatened by delays there, Governor Pataki will announce today the appointment of a redevelopment “tsar” to push the giant project forward.

A source who is close to the situation told The New York Sun last night that Mr. Pataki has asked his chief of staff, John Cahill, to bring order and results to a project that in recent weeks has appeared to be mired in chaos. Mr. Cahill, who has held the job of top adviser to Mr. Pataki since 2002, is a former commissioner of the state Department of Environmental Conservation and a longtime friend of the governor’s.

“His job is to make sure this stays on track and never goes off track,” the source, who requested anonymity, said of Mr. Cahill’s new position.

Mr. Pataki is expected to make the announcement during a scheduled luncheon of the Association for Better New York at Cipriani’s restaurant in Midtown. He has come under severe pressure to set a firm course during today’s address after reports last week that work on the Freedom Tower, the centerpiece of the redevelopment of the area attacked by terrorists on September 11, 2001, has been put off for at least several months. Mr. Pataki said last November that construction would begin in February.

The governor is also expected to announce today a new director of the agency that has overseen redevelopment at the World Trade Center site until now. The former director of the Lower Manhattan Development Corporation, Kevin Rampe, resigned only a day after a new published report suggested that the New York Police Department had tried for months to alert the Pataki administration to security concerns about the central tower.

Mr. Pataki is appointing the senior vice president for policy and programs at the LMDC, Stefan Pryor, as its new president, the source said.

In addition, NY1 News reported last night that Mr. Pataki will announce that architects have found a way to address the NYPD security concerns, and also that the LMDC would be donating hundreds of millions of dollars toward construction of the World Trade Center Memorial.

It was not clear late yesterday how Messrs. Cahill and Pryor would share responsibilities. The source simply said Mr. Cahill, a graduate of Fordham University and a father of four children, is the man Mr. Pataki turns to “when he needs to get something done.”