Kelechi Amadi, 34, was arrested early Wednesday morning when police say they interrupted the sexual attack on a bus bench in the 400 block of Santa Monica Boulevard.
His alleged victim told officers that Amadi claimed he was going to rape her.
The suspect is a registered sex offender and police are trying to locate any additional victims. Amadi was arrested for sexual battery and assault to commit rape.
If you have any information that can help investigators, call Santa Monica police at (310) 458-8495.