• Kipchoge wants to become the first man to complete the distance - 42.2km or 26.2 miles - in under two hours.
• In a video on his Twitter account, Gebrselassie said, ‘‘...believe me, you can do it’.’
Ethiopia's long-distance running legend Haile Gebrselassie has backed Kenya's Eliud Kipchoge to complete a marathon in less than two hours in his INEOS 1:59 challenge in Vienna on Saturday.
Kipchoge wants to become the first man to complete the distance - 42.2km or 26.2 miles - in under two hours.
In a video on his Twitter account, Gebrselassie said, ‘‘...believe me, you can do it’.’
Gebrselassie is a former world marathon record holder and two-time Olympic 10,000m champion. He won the Berlin Marathon four times.
Kipchoge, who won the London Marathon for the fourth time earlier this year, clocked two hours, 25 seconds in a similar attempt as part of Nike's Breaking 2 project at the Monza grand prix circuit in Italy.
This time he will run the distance over 4.4 laps of a 5.97-mile course in Prater park in the Austrian capital, with the route consisting of two 2.67-mile stretches and two small loops at each end.
The location was selected because of the favourable climate, excellent air quality and almost completely flat terrain, with only 2.4m of incline over the entire route.
But the time will not count as a world record as Kipchoge will not be running under race conditions set by the sport's world governing body, the IAAF.
The Kenyan runner told BBC Sport Africa he'll feel like the first man on the moon if he completes the course in less than two hours.