The battle for Sirte is crucial because Libya's new leaders have promised to declare liberation after it is captured even though fighting continues elsewhere and Gadhafi remains on the run.
Revolutionary forces are pushing into the Mediterranean coastal city of Sirte from the west, east and south in heavy fighting.
They said they're trying to squeeze Gadhafi loyalists into a smaller and smaller perimeter.
Residents who have fled the area said there is no electricity, water or food.
Sirte, 250 miles southeast of Tripoli, is key to the physical unity of the nation of some 6 million people, since it lies roughly in the center of the coastal plain where most Libyans live, blocking the easiest routes between east and west.
The international community has rallied around Libya's efforts to move forward with forming a new government, with transitional leaders promising elections within eight months after liberation is declared.
The Associated Press contributed to this story.