Honda chief Yusuke Hasegawa has cast doubt on whether McLaren-Honda can reach their potential this year with the 2017 specifications.
Fernando Alonso and Jenson Button endured a frustrating 2016 campaign as they tried to narrow the gap to front-runners Mercedes, Red Bull and Ferrari.
The former, alongside new team-mate Stoffel Vandoorne, look set be in for a tricky season as Honda continues to development their new power unit.
"The concept is completely different," Hasegawa told Autosport.
"It's very high risk, we don't know a lot of things about that new concept.
"We know it will give us a performance advantage but the biggest risk is whether we can realise that potential this year."
Hasegawa also revealed what Honda's main priority will be over the course of the season.
"We need to concentrate on the ICE for this year," he added.
"If we improve the engine itself, which means boosting exhaust gas energy, we need to boost the turbine otherwise we cannot perform at the same level in terms of deployment.
"We still have to do some tests and there will be some trial and error.
"I hope we have understood the direction and the elements to focus on.
"But it's not easy to combine the elements to realise the improvements on the ICE completely."