Time is running out.

A preservation group is suing the city for allowing a developer to automate one of the country’s last purely mechanical public tower clocks.

The city in 1987 landmarked the 120-year-old timepiece atop the former New York Life Insurance Company building at 346 Broadway.

A retired city employee wound the clock by hand and gave tours to the public.

The Landmarks Preservation Commission approved the sale of the landmark building and it is being converted to residences.

The clock tower would be incorporated into a triplex penthouse — and that would mean the end of the public tours.