McLaren racing director Eric Boullier says that the squad has 'seconds' of potential to unlock in its package if it can remedy the reliability issues and run on full Honda power.
McLaren has endured a troublesome first half of 2015 and has scored only five points to sit ninth in the Constructors' championship, only ahead of Manor Marussia.
Boullier is nonetheless confident that the outfit will make large gains when reliability problems can be solved.
"We all know the level of commitment from McLaren - that doesn't need to be discussed," Boullier told the official F1 website. "But the positive is the level of commitment of Honda, and the fact we know that our cars have not tenths but seconds of potential that can be unlocked.
"We cannot physically use that because we have reliability issues, but if we overcome those we will be able to make major steps forward, believe me.
"It is not completely down to only power - it has also to do with the driveability of the engine, which has proved very difficult and complex to manage so far.
"Let me give you an example: we all have the same power in terms of electrical power, but some engines are doing a better job in recovering the energy. That is why you see a difference in qualifying and the race.
"We are not able today to unlock the full recovery potential because if we do it creates reliability issues - and that hurts us in terms of performance. But it is there! We just have to find the right remedies to unlock it."