Even as President Obama endorsed military action against Muammar Gaddafi, the Libyan strongman's forces began attacking Benghazi, the heart of the rebellion. After Gaddafi reneged on his ceasefire, his troops bombarded the city with artillery and invaded with tanks, sources in Benghazi say. On the outskirts, rebels shot a fighter jet, which went down in flames. In an announcement at the White House, Obama said the U.S. would take military action against Libya if there wasn't an immediate ceasefire. However, he specified that there would be no ground invasion by the U.S., which would take a supporting role. A U.S. official said that the U.S. might take the lead in destroying Libya's air defenses at the beginning of operations. Secretary of State Hillary Clinton is in Paris to attend a meeting of world leaders Saturday to discuss military action.