The incident occurred at around 7.10pm on Wednesday (24/8) on the A418 Aylesbury Road, at the junction with Church Farm Close in Bierton.
The victim, a woman in her twenties, has been pinned to the floor with the offender grabbing her around the neck.
The offender is described as an Asian man, around 6ft tall, medium build and wearing dark clothing.
Investigating officer Sergeant Neale Simpson, based at Aylesbury police station, said:
“We would like to appeal to anybody who may have witnessed this incident or have CCTV or door cam footage in the area, to please get in touch.
“You can get in touch by either making a report online or by calling 101 quoting reference number 43220380729.
“Alternatively, for 100% anonymity, you can also call the independent charity Crimestoppers on 0800 555 111.