The Vatican said Monday that Pope Benedict XVI, who resigns on Thursday, has signed a special decree giving cardinals "the possibility to bring forward" a conclave to elect his successor.

"I leave the College of Cardinals the possibility to bring forward the start of the conclave once all cardinals are present, or push the beginning of the election back by a few days should there be serious reasons," the pope said.

The conclave is traditionally held between 15 and 20 days after the papal seat is left vacant.