Sidney Kimmel Entertainment has signed Tarsem (“The Cell”) to direct political thriller “Unthinkable,” with Kimmel and Cotty Chubb producing.

Helmer’s collaborating with British scribe Peter Woodward on revising the latter’s spec script. SKE production prexy Bill Horberg said the shingle’s hoping to launch production late in the first quarter.

“Unthinkable” is set in the contempo U.S., but the logline’s being kept under wraps.

Tarsem, a native of India, came out of the musicvid and commercial world. He directed Absolute Entertainment’s fantasy “The Fall,” which screened at the Toronto Film Festival in September.

Woodward wrote drama-romance “Closing the Ring,” which director Richard Attenborough shot earlier this year.

SKE was a producer on “United 93” and “Copying Beethoven.” Its upcoming pics include “Charlie Bartlett,” “Marriage,” “Lars and the Real Girl” and “Death at a Funeral.”