Eight-times world champion Sebastien Loeb extended his lead over Citroen team mate Mikko Hirvonen to 6.4 seconds after the second leg of the Rally of New Zealand on Saturday.
France's Loeb, who had just a four-second lead at the end of day one, battled to pad his slender advantage in slippery conditions on the technical stage on roads north of Auckland.
Norway's Ford driver Petter Solberg is in third place, more than 90 seconds off the lead.
"We've had a good battle with Mikko today," Loeb said.
"It's been difficult this afternoon, very slippery and I really don't like that Girls High School stage.
"It's very technical and I lost about eight seconds there this morning. It's exciting to have a battle with Mikko and tomorrow I will have to push to keep him behind."
The pair battled all day through the seven special stages on the roads north of New Zealand's largest city.
Loeb's lead fluctuated stage to stage, with both drivers winning two stages before Hirvonen closed the gap with victory on the final 15th Girls High School stage.
"Here we are, two days down and still in a proper fight so I'm having a good time," Hirvonen said.
"One thing is that I don't have any soft tyres left and I know Sebastien has a few, so it's going to be difficult to fight against him tomorrow."
Heavy rain is forecast for early on Sunday before it eases to showers, with the rally concluding after special stages around the Auckland Domain and a ceremonial finish on the city's waterfront.