Suncor Energy Inc (SU.TO) is in the early stages of a commercial dispute with France's Total SA over funding for the Fort Hills oil sands project in northern Alberta, the two companies said on Thursday.

The 194,000-barrel-per-day mining project is a joint venture between Suncor, Total and Teck Resources Ltd (TECKb.TO).

Earlier this year Suncor upped its Fort Hills capital costs estimate to between $16.5 billion and $17 billion, from $15.1 billion, and on Wednesday the company said it would bring forward some project spending earmarked for 2018 into this year.

Suncor Chief Executive Steve Williams said the dispute with Total was "frustrating" but will not affect plans for Fort Hills to start producing oil by the end of this year because it is already 92 per cent complete.

"We are on the final stretches. Suncor and Teck remain completely aligned in our approach to the project and I am not anticipating any impact on cost and schedule," he told analysts on a second-quarter earnings call.

Williams was asked on the call specifically whether the dispute was because they had brought forward spending and he declined to give details.

Suncor is accelerating work on Fort Hills by aiming to finish some work like hydrotesting this year instead in 2018.

Earlier this year, Total said it wrote off a portion of Fort Hills because of cost increases of the project. This was done in the first quarter, Total Chief Financial Officer Patrick de la Chevardiere told analysts in a call following Total's second quarter earnings on Thursday.

"Basically, we are not ready for a substantial cost increase in the Fort Hills mine from the operator, that is what has led to what is called a commercial dispute by Suncor who is the operator of the mine," he said.

"Despite the dispute, we are in discussion with Suncor to reduce costs," de la Chevardiere added.

Total has previously said it is looking to reduce its exposure to Canada's oil sands, which hold the world's third largest crude reserves but also carry some of the highest full-cycle operating costs globally.

Fort Hills, which was approved before oil prices started to slide in the second half of 2014, is the last of the oil sands "mega projects" to be built.

Oil sands operators like Suncor have said that in future they expect growth to come through 20,000-30,000 bpd expansions to existing projects that require less upfront capital.