Kathmandu (CNN) -- A fight for supremacy between two octogenarian climbers is heating up on the slopes of the world's highest mountain.
Eighty-year-old Japanese national Yuichiro Miura is on his way home after becoming the oldest climber to reach the summit of Everest on Thursday.
But his achievement may soon be overshadowed as his old rival, veteran Nepali climber Min Bahadur Sherchan, 81, acclimatizes at base camp, ready to reclaim his title.
The two mountaineers first clashed in 2008, when Sherchan, then 76, reached the 29,028-foot (8,848-meter) peak a day before Miura, then 75.
However, it was Miura's ascent that made it into Guinness World Records, forcing Sherchan to travel to London to set the record straight.
Back in Nepal, he gathered paperwork, photos, witness accounts and media reports to confirm his ascent, and his feat finally entered the record books in 2010.
Sherchan dismissed talk that he was making the climb because he was in danger of losing his record. He said he had planned to reach the summit last year but failed to secure financial support.
"Why should I go to set a record? I have my own record. I wanted to climb Everest in my eighth decade," he said before he left for base camp.
Mountaineering officials in Nepal said the government had waived a permit fee of $10,000 and given him about $11,200 to fund his ascent.
This year marks the 60th anniversary of the first expedition to reach the summit of Everest: Sir Edmund Hillary and Tenzing Norgay made it to the top of the mountain on May 29, 1953.
Before he boarded his flight at Kathmandu airport on Sunday, Miura said he had scaled Everest for the last time.
"I think three times is enough," said Miura, who made his first ascent at the age of 70. "At this point I could not think of anything but rest."
He wished Sherchan good luck but called on his rival to take a photograph as evidence of a successful climb.
Known for his exploits an extreme skier, Miura made the ascent with his son Gota.
Sherchan's wife, however, was less than thrilled by her husband's late-in-life mountaineering.
"Of course I do not want him to go," Purna Kumari Sherchan said. "I had told him not to go even the first time."
Sherchan is being assisted in his ascent by a Sherpa who has climbed Everest 12 times.
To prepare, Sherchan carried a 25-kilogram (55-pound) load on his back while walking up and down the stairs of his three-story Kathmandu home several times a day.
"If I am unsuccessful, it will be because of the weather. It will not be because of my physical condition," Sherchan said.
Journalist Manesh Shrestha reported from Katmandu. Journalist Katie Hunt reported and wrote from Hong Kong.