VATICAN RADIO - December 14, 2001

"Before praying the Angelus with the pilgrims gathered in St. Peter's Square, Pope John Paul, speaking from his study window which overlooks the square, invited Catholics to fast on December 14 in solidarity with those 'suffering the consequences of terrorism and war.' He also invited the leaders of the world's religions to come to Assisi on January 24, 2002 to pray for 'the promotion of an authentic peace.'"

Not sure how to fast? Try these links:
Ramadan rules and regulations
Orthodox Church fasting rules
Catholic fasting definition