Mayor Antonio Villaraigosa told Occupy LA protesters on Friday that they must leave their encampment on the lawn of City Hall by 12:01 a.m. Monday.
The mayor and police Chief Charlie Beck praised the protest and its aims at a news conference announcing the planned ouster.
"The movement has awakened the country's conscience, it has given voice to those who have not been heard," Villaraigosa said.
However, he added that from the start, he said the camp of about 485 tents was unsustainable.
"It is time to close the park and repair the grounds, so that we can restore public access to the park," the mayor said.
Occupy leaders did not immediately respond to phone messages seeking a response, but the group issued a statement Thursday saying they would reject any order from the city to leave before all of its demands are met.
Villaraigosa told campers to start packing up their tents and said he believed the move would be peaceful.
"I'm proud of the fact that this has been a peaceful non-violent protest," he said. "It is peaceful because we've decided to do things differently in Los Angeles. We've not stared each other down across barricades and barbed wire."