Rome:

(ANSA) - February 25 - Pope Benedict XVI on Monday issued a decree changing the rules of the conclave electing his successor.

The rule change allows the conclave to take place sooner than the mandatory 15 days from a papacy's end, and so before mid-March, the Vatican said.

"The cardinals will be permitted to bring forward the start of the conclave, if they are all present," said the decree, called 'motu proprio' in Latin.

Benedict, who stunned the world February 11 by announcing he would become the first pope in almost 600 years to voluntarily abdicate, steps down Thursday February 28 at 20:00 Italian time.

...Returning to the Motu Proprio, it has been established that once Conclave has started a two-third majority is required for a valid election, “calculated on the basis of the electors present and voting" and that if after three days the votes do not come to a result, "one day should be dedicated to prayer, reflection and dialogue". In subsequent rounds of voting, "only the two names which in the previous rounds had the highest number of votes will be considered, and the provision of a two third majority of the Cardinals present and voting for a valid election will remain”. Finally, the Motu proprio states that the two candidates whose names who be put forward in subsequent votes cannot vote.