The long-awaited declaration of liberation will come more than two months after revolutionary forces swept into Tripoli and seized control of most of the North African nation.
It was stalled by fierce resistance by Gadhafi loyalists in his hometown of Sirte, Bani Walid and pockets in the south.
Sirte was the last to fall, but Gadhafi's son and many of his fighters have apparently escaped, raising fears they could continue to stir up trouble.
With Gadhafi gone, however, the governing National Transitional Council was moving forward with efforts to transform the country that was ruled by one man for more than four decades into a democracy.
National Transitional Council officials had said the liberation announcement would be made Saturday in the eastern city of Benghazi, where the revolution began.
But an NTC spokesman said preparations are under way for a ceremony Sunday. No explanation was given for the delay.
Gadhafi was captured and killed by fighters in Sirte on Thursday, two months after he was driven out of power and forced into hiding.
There were conflicting reports about exactly how he died, but his final moments were caught on camera.
Libyan revolutionaries said they found him hiding in a drainage pipe in Sirte. The official word is that Gadhafi died after being caught in the crossfire of a shootout following his capture.
The 69-year-old's body was laid out on a mattress on the floor of an emptied-out vegetable freezer, and residents crowded into long lines to get a peek.
The body had apparently been stowed in the freezer in an attempt to keep it out of the public eye, but once the location was known, that intention was swept away in the overwhelming desire of residents to see the man they so deeply despised.
Gadhafi's 69-year-old body was stripped to the waist, his torso and arms streaked with dried blood. Bullet wounds in the chest, abdomen and left side of the head were visible.
It's still unknown if Gadhafi was killed in some sort of fighting or if he was executed after his capture.
A spokesman for the U.N. High Commissioner for Human Rights said the images of his last moments were very disturbing.
The Associated Press contributed to this report.