Los Angeles Mayor Antonio Villaraigosa has given Occupy Wall Street protesters in the city a deadline of midday on Monday to pack up their protest camp.
But he hopes to avoid confrontations between police and protesters that have marred evictions in other cities.
Mr Villaraigosa said he hoped for a "spirit of co-operation" with those camped out. But the BBC reports a statement from the protesters quickly rejected the deadline.
The Occupy LA camp began on 1 October, shortly after the initial protest in New York City. It has now grown to an estimated 485 tents.
Mr Villaraigosa said public health and safety could not be maintained.