President Barack Obama delivered an ultimatum to Libyan leader Gaddafi, threatening military action if he ignores demands for a ceasefire and a retreat from rebel bastions.

The US warning was immediately backed by France, Britain and Arab nations.

The US president made dramatic and forceful on-camera demands of Gaddafi, saying the world could not stand by because, if left unchecked, the Arab strongman would commit atrocities in which thousands would die.

But Obama left unclear the exact role that Washington would play in military action against Libya, beyond enabling its European and Arab partners to "effectively" mount a no-fly zone and a mission to protect civilians.

He made clear, however, that there would be no US ground troops deployed to Libya, and repeatedly stressed that the United States would not take unilateral action.

"The United States is prepared to act as part of an international coalition. American leadership is essential, but that does not mean acting alone.

"It means shaping the conditions for the international community to act together. Our goal is focused, our cause is just, and our coalition is strong."

Obama spoke as opposition rebels in the stronghold of Benghazi and other cities awaited Kadhafi's response, after it said earlier it would observe a ceasefire.

source: AFP