Tanak headed to the final service of the gravel event with a slightly reduced 51.6s lead over Hyundai’s Teemu Suninen.
Suninen came under pressure from charging Hyundai team-mate Thierry Neuville (+58.3s), who won the morning’s two stages.
Toyota’s Elfyn Evans completed the loop in fourth overall (+1m19.1s) ahead of title rival Kalle Rovanpera (+2m07.8s), with the third Toyota driven by Takamoto Katsuta in sixth (+4m42.4s).
Sunday began with a fast yet technical pass through stage 13 (13.20km) held in overcast conditions.
Rally leader Tanak could afford to opt for a measured approach having built up lead of more than a minute. He successfully navigated the test without issue, albeit 10.8s slower than pacesetter Neuville, as his overall lead was trimmed to 52.3s.
Keen to overhaul team-mate Suninen to claim second overall, the Belgian took the stage win by 4.8s from his Hyundai stablemate to reduce the gap to 9.1s.
"I had a good stage, I enjoyed it. A couple of small moments, I was on the limit on many corners but the car was working nice so I enjoyed the ride," said Neuville.
Evans’ hopes of stealing third were dealt a blow as he couldn’t match Neuville’s speed and dropped five seconds. Title rival Rovanpera, celebrating his 23rd birthday, remained in fifth overall after clocking the fifth-fastest stage time.
There was however drama for M-Sport Rally1 debutant Gregoire Munster before the stage begun as he was involved in a road traffic accident that left his Puma with minor damage.
"Just before the refuelling out of the service we had a road accident with a car, so we were a bit scared with the right side," said Munster.
Stage 14 (El Ponen, 13.86km), a dress rehearsal for the rally-ending Power Stage followed and it was again claimed by Neuville. The Hyundai driver beat team-mate Suninen by 2.4s, leaving only 6.7s separating the pair heading into the final loop.
Tanak was third-fastest with Evans and Rovanpera coupleting the top five stage times.
In WRC2, Toksport Skoda driver Oliver Solberg maintained his lead over team-mate Gus Greensmith to hold seventh and eighth positions overall.
