The famous Hollywood sign is expected to be replaced by an environmental message — if only for a day.

Trust for Public Lands, a nature conservation group, says it has reached a deal to protect a swath of land above the sign from being developed into luxury homes. To mark the deal, and draw attention and money to the cause, the group wants to cover up the sign for a day with a shroud reading: "Save the Peak."

The group is still waiting for permission from the city for the one-day sign change on Thursday, but the Los Angeles Police Department already has sent out an alert to neighborhood residents so they wouldn't be alarmed.

The president of Trust for Public Lands, Will Rogers, said the group secured an option to buy the 138-acre parcel for about $12 million from a Chicago-based firm. Rogers said the conservation group has already raised $6 million and is confident it can raise the rest of the money before the option expires in mid-April.

If the group succeeds, it intends to transfer the land to the city of Los Angeles, so it can be incorporated into the adjacent Griffith Park.

City officials and many residents say that building homes on the peak would ruin one of the city's most famous views.

"The city of Los Angeles wants to acquire this land, not only to maintain the view of the Hollywood sign, but also to preserve open space, hiking trails and wildlife corridors for the future health of our great city," Councilman Tom LaBonge, whose district includes Cahuenga Peak, said in a statement.

If the conservation group fails to raise the final $6 million before April 14, the property will go back for sale on the open market.

"There's always a concern when you have a deadline," Rogers said. "I'm optimistic, but there's always that chance."

The Associated Press contributed to this report.

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