Sen. Mary Landrieu said Tuesday she has blocked Senate confirmation of the nominee to head of the Army Corps of Engineers to allow time for debate on his role in rebuilding hurricane-ravaged Louisiana.

Landrieu, D-La., said she had placed a "procedural hold" on the nomination process for Lt. Gen. Robert Jan Antwerp Jr.

His credentials are not in question, she said in a statement, but she wants to determine if Antwerp will be "the partner we need for the recovery and protection of our region, or will he be the agent of a failed status quo?'"

The corps has come under criticism for installing drainage pumps to protect New Orleans in spite of apparent deficiencies.

Landrieu has asked the Government Accountability Office, Congress' investigative and auditing arm, to investigate if there was improper influence in the way the pumps contract was awarded and handled. She also wants to know what danger the pumps posed to New Orleans, and the Corps' rationale for installing them.

The Corps has said it decided to install the pumps, and then fix the machinery while it was in place, believing that some pumping capacity was better than none. It also has defended the manufacturer, which was under time pressure.

A state-commissioned report said last month that the Corps of Engineers was solely responsible for decades of mistakes that led to levee failures and the devastating flooding of New Orleans after Hurricane Katrina.

"Given the significant involvement of the U.S. Army Corps of Engineers in the rebuilding of Louisiana, I feel that this nomination will require extended discussion and debate," Landrieu said.