Apa Sherpa unfurls a Nepalese national flag on the summit of Mount Everest on May 11. The Nepalese climber who has conquered Mount Everest a record 21 times, says he plans to embark on a gruelling 1,700 kilometre (1,060-mile) trek across the Himalayas

Apa Sherpa unfurls a Nepalese national flag on the summit of Mount Everest on May …

Apa Sherpa, the Nepalese climber who has conquered Mount Everest a record 21 times, announced Wednesday plans to embark on a gruelling 1,700 kilometre (1,060-mile) trek across the Himalayas.

The 51-year-old father of three, dubbed "Super Sherpa", will set off in January on the 120-day walk with climber Dawa Steven Sherpa in a bid to raise awareness of climate change.

The expedition, the first official hike along the length of Nepal's Great Himalayan Trail since it opened in September, will take in some of the world's most rugged landscapes and see the duo ascending beyond 6,000 metres (19,600 feet).

"The Great Himalaya Trail is possibly the world's best long-distance walking trail," Apa Sherpa said, describing the adventure as a "once-in-a-lifetime opportunity".

The route extends along the length of the Himalayas in Nepal, passing in the shadow of eight of the world's 10 highest mountains.

The expedition has been dubbed the Climate Smart Celebrity Trek and the duo said they hoped to be accompanied along parts of their journey by Hollywood and Bollywood stars, although organisers admitted none had yet signed up.

Apa Sherpa, who was born in Nepal but now lives in the United States, first scaled 8,848-metre Everest in 1990.

He has spoken of the dramatic changes to Everest in the past two decades, and after an expedition last year said rising temperatures were making the mountain increasingly dangerous for climbers.

The climber has dedicated his last four ascents to efforts to preserve Everest, which the Sherpa people consider sacred, and this year climbed with a team removing tonnes of rubbish left behind by earlier climbers.

Last year, he set up a foundation dedicated to improving education in the remote Himalayan region where he grew up.