Friday's leg from San Juan to Rio Cuarto was the last real chance for rivals to attack.
"We're here, we're safe and we have just one more day of the Dakar," said 27-year-old Sunderland, who was fifth on the stage. "I think the gap is around 30 minutes. I'd like it to be three hours, but it's better than 30 seconds.
"Victory is starting to creep into the mind a little bit and I'm trying to fight it away and stay focused on the job," he added.
"It's hard to explain the things that go through your mind when you're on the bike for 12 to 14 hours a day on your own. You start to have all kinds of crazy thoughts. It's not easy to keep them quiet and focus on the job."
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The final stage is in Rio Cuarto before the caravan heads to Buenos Aires for the official finish and podium ceremony.
Peterhansel has seen it all before, with six wins on bikes and another six in cars, and he finished the day with a five minutes 32 seconds lead over Peugeot team mate Sebastien Loeb.
Loeb, a nine times world rally champion, won the stage -- his fourth win of this year's event -- despite a late puncture.
"We had to change the wheel and Stephane passed us. We didn't try so much after that, because it was lost. I think the gap is too big for the short stage tomorrow," said the Frenchman.
Peterhansel, who regained the lead from Loeb on Thursday, paid tribute to his compatriot.
"In the end, it was a nice fight. It is really an honour for me to fight with Sébastien Loeb ... he's my team mate and we have a lot of respect: The spirit is really good."
The Dakar Rally began 1978 as a gruelling race from Paris across the Sahara to the Senegalese capital but switched to South America in 2009 for security reasons.
(Reporting by Alan Baldwin in London, editing by Peter Rutherford)
