The woman was walking along the cycle path between Haverfordwest and Tiers Cross when she was approached by a man who threatened and assaulted her, before walking away towards Haverfordwest town.
The male is described as a white male, between 5ft 4 and 5ft 11 tall , normal build with a Welsh accent. He has short dark hair, a beard and a moustache, brown eyes, and wearing light blue jeans, navy/dark blue jersey with grey sleeves.
Anyone who saw a man matching this description in the area between 3.30pm and 5pm on the afternoon of Sunday 16 May is asked to contact police.
A 35-year-old man has been arrested and is currently in police custody.
The cycle path is currently closed while the investigation continues.
Detective Superintendent Jayne Butler, who is leading the investigation, said: “Incidents of this nature are extremely rare in the Dyfed-Powys area.
“The public may see an increased presence of police officers in the coming days as police investigate the incident.
“Anyone with concerns or information that could help our enquiries can speak to those officers or contact police.
“While a man was quickly arrested we would still like to speak to anyone who saw a man matching the above description in the area yesterday afternoon.”
Anyone with information which could help the investigation is asked to contact police online, by emailing 101@dyfed-powys.pnn.police.uk, or by calling 101.
