Police are beginning a retrieval operation in bushland in the Blue Mountains west of Sydney after the reported sighting of a body believed to be that of missing man Gary Tweddle.

NSW Ambulance officers on a helicopter training exercise reported seeing a body in bushland near a rock climb off Sublime Point Road at Leura about 4pm (AEST) on Monday.

Police attached to the Blue Mountains Local Area Command will abseil down to the site on Tuesday, as it is inaccessible by foot.

At this stage, police say they're unable to confirm that it is a body.

"We're concentrating on an area around 50m from the top of the cliff line, in what you would describe as a slot in the cliff face," Blue Mountains Local Area Commander Darryl Darryl Jobson told ABC radio on Tuesday.

He said it may take some hours before rescue officers can access the site.

Commander Jobson said the area was full of dense bushland and the cliff face had a 300 metre vertical descent.

The site the police rescue team will be attempting to reach is about 2km from where Mr Tweddle was last seen before going missing from a work conference at Leura resort in mid-July.

He had called colleagues about midnight to tell them he was lost in bushland but could see a light up a hill.

Ten days after the 23-year-old disappeared, the search for him was scaled back to a recovery operation.

Mr Tweddle's family, who have spent the past six weeks helping with the search, have been kept up to date about the latest developments.

Last week Mr Tweddle's partner Anika Haigh said that a report had been filed to the coroner in which investigators listed his disappearance as an accidental death.

"The disappearance of the most beautiful, loving, kind and caring man has left me, family, friends, colleagues and the community utterly devastated," she wrote on the Facebook page titled, `Have you seen Garry Tweddle?'.

"Our hearts ache for the partner, son, brother, nephew, cousin, uncle, friend and colleague that we no longer have in our everyday lives."