Meyer on Libya: 'Possible humanitarian disaster'
Opposition fighters in Libya say they have pushed back troops loyal to Colonel Gaddafi from the town of Ajdabiyah - 80 miles west of the rebel stronghold, Benghazi.
The Libyan army has warned people in Benghazi to stay away from buildings and other areas being used by the rebels.
The US government has said it will support a no-fly zone over Libya.
The United Nations Security Council is expected to vote on Thursday on a resolution backing such a zone - but it's not clear whether all countries on the Council will support such a move.
A former British ambassador to Washington, Sir Christopher Meyer, said the international community needed to act quickly and decisively.