Police are calling on the public to help identify a man they believe to be a suspect in the Dec. 14 robbery of a 17-year-old on a Q train in Sheepshead Bay.

Police say the man pictured with dreadlocks and a blue coat allegedly demanded the 17-year-old give him his phone at knifepoint as the train pulled into the station around 1 p.m., before robbing him a second time on the platform for his backpack and his sweatshirt.

The footage released to the public comes from the new universal camera system deployed on every train car citywide.

Anyone with information is asked to call Crime Stoppers at 1-800-577-TIPS (8477). All calls are strictly confidential.