"Muammar Gaddafi has lost legitimacy to lead, and he must leave," Obama said at a White House news conference.
The US president said, the "violence must stop...Those who perpetrate violence against the Libyan people will be held accountable... The aspirations of the Libyan people for freedom, democracy and dignity must be met."
"I have approved the use of US military aircraft to help move Egyptians who have fled to the Tunisian border to get back home to Egypt," he added. Thousands of people from many different countries are fleeing Libya.
"We commend the governments of Tunisia and Egypt for their response, even as they go through their own political transitions," he added.
Obama said that he has also authorized USAID to charter additional civilian aircraft to help people from other countries find their way home. "We are supporting the efforts of international organizations to evacuate people as well," he said.
He has also directed USAID to send humanitarian assistance teams to the Libyan border, so that they can work with the United Nations, NGOs and other international partners inside Libya to address the urgent needs of the Libyan people.
With respect to America's willingness to engage militarily, Obama said he has instructed the Department of Defense, and the State Department to examine is full range of options.
"I don't want us hamstrung. I want us to be making our decisions based on what's going to be best for the Libyan people in consultation with the international community," he said.
"We are doing that not just here in the United States within our own agencies, but we're also doing it in consultation with NATO," he said.
"There may be situations in which Gaddafi is hunkered down in his compound but the economy -- or food-distribution systems in Tripoli, for example, start deteriorating. And we''re going to have to figure out how do we potentially get food in there," Obama said.
"So there are a whole range of options, military and non-military, that we're examining. We we''ll be making these decisions based on what's best for the Libyan people and how can we make sure that we''re minimizing the harm to innocent civilians during this process," he said.
"Those around him have to understand that violence that they perpetrate against innocent civilians will be monitored and they will be held accountable for it."
"So to the extent that they are making calculations in their own minds about which way history is moving, they should know history is moving against Colonel Gaddafi and that their support for him and their willingness to carry out orders that are direct violence against citizens is something that ultimately they will be held accountable for," he said.