Still, Obama also said the United States "is not going to deploy ground troops into Libya."
In a brief appearance at the White House, Obama said Secretary of State Hillary Rodham Clinton would travel to Paris on Saturday to join in a meeting of allies called to discuss next steps in Libya, where Gadhafi has launched a brutal crackdown against rebels trying to end his 42-year reign.
Obama's remarks came less than 24 hours after the United Nations Security Council voted to authorize military action to prevent the killing of civilians by Libyan forces.
There should be no doubt about Gadhafi's intentions "because he has made them clear," Obama said. "Just yesterday, speaking of the city of Benghazi, a city of roughly 700,000, he threatened 'we will have no mercy and no pity.' No mercy on his own citizens."
The president has been criticized by U.S. lawmakers and others for not moving more forcefully while Gadhafi has regrouped in recent days and taken the offensive against the rebels. Obama said the United States and other nations have imposed sanctions on Libya, frozen assets of the leader and delivered humanitarian supplies to bordering countries to help ease the plight of thousands fleeing the fighting.
"Now, once more, Moammar Gadhafi has a choice," Obama said, listing what he said were non-negotiable conditions laid out by the U.N. Security Council.
"If Gadhafi does not comply, the international community will impose consequences, and the resolution will be enforced through military action," Obama said.