The Toyota driver led Norwegian Andreas Mikkelsen, in a Hyundai, and Citroen's Finnish driver Esapekka Lappi who were tied 54.5 seconds behind.
Belgian Thierry Neuville, also in a Hyundai, was a further 2.3 adrift.
Sunday's final leg involves just three stages and a total 51.3km of timed action.
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Overnight leader Teemu Suninen lost more than a minute after going into a snow bank early in the day, handing the lead to Tanak. The M-Sport Ford driver later crashed into a tree and retired.

Ott Tanak and Martin Javeoja from Estonia in Toyota Yaris WRC compete during day 2 of the second round of the FIA World Rally Championship, Rally Sweden 2019, in Karlstad, on February 15, 2019

Image credit: Getty Images

"This afternoon the grip changed at every corner and you never knew what to expect. Hopefully we can control things a bit tomorrow, but it’s never an easy ride," commented Tanak.
Six-times world champion Sebastien Ogier, winner of the Monte Carlo opener last month, returned to the fray after getting his Citroen stuck in a snow bank and retiring on Friday.
The Frenchman won three of the day's stages but was way back in 33rd place.
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