Honda has been working on significant revisions to its V6 engine in a bid to close a significant power deficit to leading F1 engine manufacturers Mercedes and Ferrari.

Honda has been struggling to successfully transfer experimental combustion technology from a single cylinder to six on its Sakura dynos without encountering problems.

It has sought extra help from independent engine consultant Ilmor and reportedly sounded out Mercedes too as part of a concerted effort to accelerate progress.

Although Honda originally hoped to have its first major performance update ready before next month, Hasegawa says he cannot be sure the update won't be delayed until after Canada.

"Obviously Canada will be the power circuit, so if we can prepare the new engine, we'd like to," Hasegawa said.

"But still I'm not sure that we can."

The Japanese firm has only changed engine maps and made reliability tweaks so far this season, though introduced revisions to its induction and fuel system for Barcelona that Honda says has almost eliminated the driveability problems that have also hurt McLaren-Honda's form over the first four races of 2017.

"Here the engine component is the same but there is an updated induction system and fuel system," Hasegawa added.

"The upgrade is a quite decent level of upgrade, but [with] the current gap to the top teams, we cannot be proud too much."

The 2017 Honda engine has been plagued by unreliability issues since first running in pre-season testing, with Stoffel Vandoorne forced to serve a grid penalty in Russia, Alonso failing to finish the last two races thanks to engine problems, and a further failure of his combustion engine forcing the Spaniard to stop on his first lap in Friday practice for this weekend's race in Spain.

Hasegawa said a mechanical problem with the oil system led to Friday's failure and he is confident there won't be a repeat in the race, where Alonso will start seventh after making Q3 for the first time this season.

"From the data we lost the oil first so the pressure went down and still the engine was running, so the engine was OK, but once the oil pressure was down then the engine was broken," Hasegawa explained.

"We are thinking the oil pressure drop was happening from some mechanical issue with the oil feed."