WBRZ - Baton Rouge

VATICAN CITY - Pope Benedict XVI has greeted his cardinals for the last time as pontiff, beginning his final day as leader of the world's 1.2 billion Catholics before heading into retirement.

During his comments, Benedict promised "unconditional reverence and obedience" to his successor.

He urged his cardinals to work in unity so that the College of Cardinals is "like an orchestra" where "agreement and harmony" can be reached - a clear message to the conclave that will pick the next pope.

He said he would pray for the cardinals in coming days and weeks as they choose his successor.

Around 5 p.m., Benedict will leave the palace for the last time as pontiff, head to the helicopter pad on the hill in the Vatican gardens and fly to the papal retreat at Castel Gandolfo.

There, at 8 p.m. sharp, Benedict becomes the first pontiff in 600 years to resign. The doors of the palazzo will shut and the Swiss Guards in attendance will go off duty.