But Gadhafi has refused to step down, going so far this week as to do a live audio broadcast as NATO warplanes bombed his Tripoli compound.
"We will not surrender," he said during the broadcast.
Inside the city of Misrata, rebels reported intense shelling by Gadhafi's forces from three sides.
It was the bloodiest day of fighting in a week, said Dr. Khaled Abu Falgha, a spokesman at Misrata's Hekma hospital.
More than 1,000 people are believed to have been killed since the fighting began there in early February, including 686 civilians who lived in the city, he said.
Misrata has been under siege for months by Gadhafi's forces, who have cut off all land access. The only escape route for rebels and civilians is by sea.
Rebel fighters said their defense of Misrata was holding.
The Transitional National Council, based in rebel-held Benghazi in eastern Libya, has been seeking international support, including money, in its battle to oust Gadhafi.
Secretary of State Hillary Clinton was expected to attend a meeting in the United Arab Emirates of the Libyan Contact Group, a coalition of various countries and international organizations that seek to build support for the rebel government.
France, Italy and Qatar are among a small number of countries that have recognized the Transitional National Council as the legitimate government of Libya.
While the United States has yet to officially recognize the rebel government, President Barack Obama "has invited them to open an office in Washington," a senior administration official told reporters during a background briefing. The reporters were traveling with Clinton to the Abu Dhabi meeting.
The official spoke on condition of anonymity as a matter of practice for such a briefing.
Meanwhile, the International Criminal Court's chief prosecutor said a decision was expected within days from judges at the Hague on whether to charge Gadhafi and two others with crimes against humanity.
Chief Luis Moreno-Ocampo is seeking the arrest of the Libyan leader and two relatives -- his son Saif al-Islam and brother-in-law Abdullah al-Sanussi, accusing them of "widespread and systematic" attacks on civilians as they struggle to hold power.
Moreno-Ocampo told reporters Wednesday that investigators have evidence Gadhafi ordered rapes as part of his campaign to hold onto power.
