VAL DI FIEMME, Italy (AP) -- Petter Northug revved up his preparations for next month's Sochi Olympics by winning the penultimate stage of the Tour de Ski on Saturday, cutting into the overall lead of fellow Norwegian Martin Johnsrud Sundby.
Northug clocked 24 minutes, 45.6 seconds over the 10-kilometer classical stage. Sundby crossed second, 9.7 seconds behind, and Chris Jespersen, yet another Norwegian, was third.
Sundby's lead over Northug was reduced to 48.5 seconds, with Jespersen 1:26.8 behind entering Sunday's seventh and final stage, the grueling climb up Mount Cermis.
The top American is Noah Hoffman in 31st.
Norwegians are also commanding the women's race, with two-time runner-up Therese Johaug winning a 5K classical stage to cut into the lead of countrywoman Astrid Uhrenholdt Jacobsen.
Johaug timed 13 minutes, 58.4 seconds to finish 14.9 seconds ahead of Jacobsen, with Anne Kyllonen of Finland third, 19.2 back.
In the overall, Jacobsen's lead over Johaug was sliced to 23.8 seconds, with Kyllonen 1:31.5 back.
The top American is Jessica Diggins in 11th.
Northug won the 15K classical title at last year's world championships in Val di Fiemme and also took gold in the 50K at the 2010 Vancouver Olympics. He has also finished on the podium four times in the Tour de Ski but has never won the competition.
''I am getting stronger with each competition,'' Northug said. ''This time I am not as tired going to the final stage.''
Sundby has never come close to winning the Tour de Ski.
''I felt quite tired after yesterday's competition,'' said Sundby, who won Friday's stage. ''I felt better in the second lap. I have to recover well today and get ready for the final climb. It will be pure pain.''
Johaug was runner-up in 2011 and 2013 and finished third in 2012, while Jacobsen has never reached the podium.
''I feel I am in a very good shape and I can compete with almost everybody,'' Jacobsen said. ''I do not think much about the overall result. It's already a great achievement for me to be in the leading position before the final stage. I am happy that there is a high chance that a Norwegian lady crosses the finish on Alpe Cermis in first place.''