The man's body was spotted by an ambulance rescue helicopter in a tree growing out of a crevice in a cliff at Leura on Monday afternoon.

A police officer at the scene said a striped shirt found near the body matched the description of the one Mr Tweddle was wearing on the night he went missing.

It is seven weeks to the day since the 23-year-old, from Cremorne on Sydney's north shore, vanished from the Fairmont Resort at Leura.

Officers abseiled down a cliff at the end of Sublime Point Road and were working to secure the body about 1.30pm on Tuesday.

They plan to carry the body to the top of the cliff, where it will be transferred to a helicopter.

Superintendent Darryl Jobson said it would be several hours until the body was recovered and many more until the body was formally identified.

"I can confirm we have found a deceased male ... in what's described as a slot in the cliff line," Superintendent Jobson said.

Police said no items were found on the deceased.

Superintendent said police were in close contact with the family.

"The family have been very strong and stoic throughout. It's absolutely amazing to see the strength they've been able to garner from each other."

"They have gone through a rollercoaster of emotions, as you can well appreciate.

"They are really after a sense of closure."

Mr Tweddle's girlfriend Anika Haigh, 23, her sister and mother are in the Blue Mountains waiting anxiously for confirmation.

"The sun is beginning to rise on a day that we have all been hoping would never come," she posted on Facebook.

"Please know that nothing has been confirmed at this stage but I hope in a few hours we will have an answer either way," Ms Haigh wrote on Facebook.

"One thing I know for certain is that Gary will come home one day - his fight, determination & 'never give up' attitude that we all loved so much about him will guide him."

She said Gary's disappearance had left a hole in her life, but her heart was full of "amazing memories of you".

"Your time of hide & seek needs to end now though please. Time to come home where you belong. I love you," she wrote.

An ambulance rescue helicopter was involved in a training exercise about 4pm on Monday when the crew spotted a body near a rock climb known as Sweet Dreams off Sublime Point Road, near Leura.

Mr Tweddle's disappearance sparked the biggest search ever conducted in the Blue Mountains, with more than 1000 volunteers involved.

The British-born computer sales representative, from Cremorne on Sydney's north shore, disappeared from the resort, where he had been attending a work conference, in the early hours of July 16.

A taxi dropped him off at the resort after he had been to dinner at Silk's Brasserie in Leura.

Security footage showed him running out of the main foyer without his jacket or glasses just after midnight.

Mr Tweddle told work colleagues he was lost during a 17-minute phone call. He was last seen by a motorist on Watkins Road.

Gary's brother, Craig, wrote on Facebook that it was extremely likely that the body was that of his brother.

"I will be there to scatter your ashes on land you called home don't worry mate you're staying in Aussie. we will have a stone for you here in the UK," he wrote.