NSW Police have released a drawing of a man they wish to speak to about a sexual assault investigation.

Police allege a woman was walking along Missenden Road, in the inner Sydney suburb of Camperdown, when she was grabbed by a man, pulled into a nearby laneway and sexually assaulted at 1.30pm on Sunday, February 11.

Detectives have released a computerised image of a man who they believe can help with their investigation.

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The man is described as being Caucasian in appearance with short slicked-back brown hair, aged in his 60s.

He is believed to have been wearing a black singlet, black tracksuit pants and thongs at the time of the alleged attack.

Anyone with any information is urged to come forward and contact police or Crime Stoppers.