British explorer Sir Ranulph Fiennes has had to abandon his effort to climb Mount Aconcagua in Argentina after suffering severe back pain.
The mission was part of the 72-year-old's record-breaking challenge for the charity Marie Curie.
Sir Ranulph was aiming to become the first person to cross the North and South Poles and climb the highest mountain on each of the world's seven continents.
He said he is "very frustrated".
Mount Aconcagua is the highest mountain in South America, standing 6,959m high.
"I was within just a few hours of the summit but problems with my back meant I couldn't continue," he said.
"I've learnt that at my age you can't ignore any pain. I'm going to come home to the UK and get my back looked at before I do anything else."
He has already climbed Mount Elbrus in Europe, Mount Everest in Asia, Mount Kilimanjaro in Africa and, just last month, he finished climbing Mount Vinson in Antarctica.
It is not yet clear if the explorer from Exmoor, Somerset, will go ahead and climb the last two mountains of the challenge, Mount Carstensz in Australasia and Mount Denali in North America.