Flexing its military muscle, the United States sent warships toward Libya on Tuesday as it sought to keep pressure on Muammar Gaddafi to relinquish his four-decade grip on power.
Secretary of State Hillary Clinton said the United States and its Nato allies were still considering a 'no-fly' zone over Libya, although military commanders warned of the peril to allied aircraft of enforcing it.
The United States has also frozen $30 billion in Libyan assets.
"We are going to keep the pressure on Gaddafi until he steps down and allows the people of Libya to express themselves freely and determine their own future," Susan Rice, the U.S. ambassador to the United Nations, told ABC's 'Good Morning America' program.
Two amphibious assault ships - the USS Kearsarge, which can carry 2,000 Marines, and the USS Ponce - were due to sail through the Suez Canal and enter the Mediterranean Sea early on Wednesday morning, an Egyptian official said.
The repositioning of U.S. ships and aircraft closer to Libya is widely seen as a symbolic show of force since neither the United States nor its NATO allies have shown any appetite for direct military intervention in the turmoil that has seen Gaddafi lose control of large swaths of his country.
U.S. officials said the ships were being redeployed in preparation for possible humanitarian efforts as tens of thousands of people flee the violence. But they said military action remained an option.
"We are looking at a lot of options and contingencies. No decisions have been made on any other actions," Defense Secretary Robert Gates said, noting the United Nations had not authorized the use of force in Libya.
As of Tuesday, there were three U.S. ships in the Mediterranean - two destroyers and the USS Mount Whitney, the command ship of the U.S. Sixth Fleet based in Gaeta, Italy.
Gates declined to comment on reports the USS Enterprise, an aircraft carrier in the Red Sea, could be moved into the Mediterranean, a step that would significantly augment the U.S. military presence off Libya.