The mayor of Los Angeles has given Occupy Wall Street protesters in the city a deadline of Monday morning to pack up their protest camp.
But he hopes to avoid confrontations between police and protesters that have marred evictions in other cities.
Mayor Antonio Villaraigosa issued the deadline of 12:01 on Monday (08:01 GMT), saying he hoped for a "spirit of co-operation" with those camped out.
A statement from the protesters quickly rejected the mayor's demand.
"As a collective, Occupy Los Angeles would like to express their rejection of the city of Los Angeles's alleged proposal that we leave City Hall," protester Jeremy Rothe-Kushel told the Associated Press.
Police will be in City Hall Park over the weekend to forewarn protesters, city officials said on Friday.
Despite issuing the deadline, Mr Villaraigosa spoke about the Occupy movement in terms not often heard from elected officials in the US.
"The movement is at a crossroads," the mayor said. "It is time for Occupy LA to move from holding a particular patch of park land to spreading the message of economic justice and signing more people up for the push to restore the balance to American society."
However, the camp - which has now grown to an estimated 485 tents - was unsustainable because public health and safety could not be maintained, he said.
Using a refrain familiar to protesters from New York, where Mayor Michael Bloomberg complained about the health impact of the Zuccotti Park camp, Mr Villaraigosa said City Hall Park had to be cleared, cleaned and restored for public access.
"I'm proud of the fact that this has been a peaceful, non-violent protest," he said. "I trust that we can manage the closure of City Hall Park in the same spirit of co-operation."
The Occupy LA camp began on 1 October, shortly after the initial Occupy protest in New York City.
Protests in the city have been largely peaceful, with fewer tensions between police and those camping out than in some cities.
In Oakland, California, there were several flashpoints between police and protesters, and police also used pepper spray in breaking up an Occupy camp in Seattle, Washington.