A trapped caver awaiting rescue after becoming seriously ill 3,000ft underground has appeared in a new video saying he had been "close to the edge" before the arrival of vital medical supplies.

Mark Dickey, 40, suffered gastrointestinal bleeding on Saturday inside the Morca Cave in southern Turkey, which is around 4,100ft (1,276m) deep.

The US man fell ill close to the bottom of the crevice at 3,670ft (1,120m) and was later moved to a campsite at a 3,400ft (1,040m) depth.

Rescuers have managed to get medical supplies and units of blood to Mr Dickey, who said he is "alert" and "doing well".

However, speaking in a new video from the underground campsite, the researcher said: "I'm not healed on the inside yet, so I'm going to need a lot of help to get out of here.

"I do know that the quick response by the Turkish government to get the medical supplies that I needed, in my opinion, saved my life.

"I was very close to the edge when Jessica [my fiancée] got back to me.

"I look forward to working with everyone to safely get myself out with their assistance."

The footage was released by Turkish authorities.

'Complex and lengthy' operation

It takes around 15 hours for an experienced caver to reach the surface of the Turkish cave - which includes narrow winding passages and several rappels (rope descents down very steep slopes) in ideal conditions.

The international rescue effort is said to be one of the largest cave rescue operations in the world, both logistically and technically.

Image:Rescue teams at the mouth of the Morca Cave

Image:Around 150 people have been deployed to help bring Mr Dickey to safety

It involves around 150 people from across Europe including Italy, Hungary, Croatia, and Bulgaria.

Communication takes about five to seven hours and is carried out by runners, who go from Mr Dickey to the camp below the surface, where wire communication to talk to the surface has been set up.

Mr Dickey is an instructor with the US National Cave Rescue Commission (NCRC), who is highly regarded in the international speleological (the study of cave exploration) community and has previously taken part in rescue missions.

He was co-leading an expedition to find and map a new passage in the Turkish cave, the third deepest in the country, when he fell ill.

'Devastatingly scary situation'

Mr Dickey has his fiancée and fellow caver, Jessica, at his side, according to a statement by his parents, Andrew and Deborah Ann Dickey.

Image:Mark Dickey

Sky News' US partner, NBC News, reports that Mr Dickey's family said in a statement: "Mark is strong, but he needed his fellow cavers, including, of course, the doctors, to allow a devastatingly scary situation to turn positive.

"Our prayers are being answered and we cannot express how much that means, and will always mean, to us."

A fundraising campaign has also been launched by the NCRC to raise money for the efforts to rescue Mr Dickey, which has so far raised $41,000 of its $100,000 target.