WASHINGTON President Barack Obama said on Thursday he was concerned a bloody stalemate could develop between Libyan leader Muammar Gaddafi and rebel forces but gave no sign of a willingness to intervene militarily.
Rebels seeking to overthrow Gaddafi have called for U.N.-backed air strikes against what they say are African mercenaries launching assaults on Libyans to help keep the longtime ruler in power.
Calls for a "no-fly" zone over the oil-producing North African nation have also come from several senior members of the U.S. Congress.
Obama said he had asked his military and diplomatic advisers to examine "a full range of options" and that a no-fly zone was one of those.
"I don't want us hamstrung," he said. "I want us to be making our decisions based on what is going to be best for the Libyan people in consultation with the international community."
Obama, speaking at a news conference with Mexican President Felipe Calderon, emphasized the importance of humanitarian efforts as he expressed outrage at the bloodshed in Libya and called on Gaddafi to step down.
Obama offered the use of U.S. aircraft to help move Egyptians now stranded at the Libyan border with Tunisia and to help refugees from other nations who are fleeing Libya.
An organized international airlift relieved the pressure of a surge of people from Libya into Tunisia on Thursday after three days of chaos. France was providing six flights per day and British charters began a shuttle to Egypt.
Defense Secretary Robert Gates on Wednesday warned against "loose talk" about a no-fly zone.
"Let's just call a spade a spade. A no-fly zone begins with an attack on Libya to destroy the air defenses," Gates said.
He and other officials have listed logistical and diplomatic hurdles to such action.
"HE MUST LEAVE"
Opposition is intense among Arab states to foreign intervention in Libya. Administration officials also worry about being drawn into further foreign military operations as Obama seeks to wind down the wars in Iraq and Afghanistan.
Thursday marked the first time Obama has called in public for Gaddafi to leave Libya, although he has urged his exit in written statements issued by the White House.
"We will continue to send a clear message: The violence must stop. Muammar Gaddafi has lost the legitimacy to lead and he must leave," Obama said.
He also issued a warning to any of Gaddafi's officials found to have been promoting attacks on Libyan citizens.
"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," he said.
U.S. officials showed little enthusiasm for a plan by Venezuelan President Hugo Chavez, a Gaddafi ally, for international mediation to end the standoff between the Libyan leader and the rebels.
"It uncertain to me what an international commission is going to accomplish. Colonel Gaddafi needs to step down," State Department spokesman P.J. Crowley said.
U.S. lawmakers were also wary.
Richard Lugar, the top Republican on the Senate Foreign Affairs Committee, said Chavez's "doubtful" credentials on democracy made him the "least objective or desirable actor" to mediate on Libya.
"A negotiated settlement would mean that Gaddafi would get some concessions that he doesn't deserve," said Ileana Ros-Lehtinen, the Republican chairwoman of the House Foreign Affairs committee.
(Additional reporting by Caren Bohan, Steve Holland, Missy Ryan, Andy Quinn and Susan Cornwell; Editing by John O'Callaghan and Paul Simao)