A 28-year-old woman was walking on West 51st Street in Midtown on Thursday just before noon when she was approached by the suspect.
Police say the man grabbed her by the neck and threatened her with a box cutter, demanding her valuables.
The suspect searched her pockets and stole her cellphone before running away.
The victim was not seriously hurt.
Anyone with information is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
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