McLaren is likely to have both cars start this weekend's Azerbaijan Grand Prix from the back of the grid, as Honda brings a first step update to their struggling power unit.

The British team was already bracing for another difficult event in the Eurasian country, with the 2.2-kilometre main straight as well as a mix of slow and high-speed corners again expected to fully exploit the lack of power and efficiency from the Japanese manufacturer's engine.

At a similar type of circuit in Canada just over a week ago, Fernando Alonso was able to remain somewhat competitive, running 10th before being forced to retire two laps from the end.

However, due to the likely penalties, the platform the Spaniard was able to build that race performance on will almost certainly not exist.

"We go to Baku with even more determination, but it’s no secret that we expect to find this weekend tricky,” the double world champion conceded.

“After the power unit issues it’s likely we’ll need to take penalties and the nature of the narrow, fast straights and tight corners means overtaking is generally tough. However, it’s certainly not impossible, and we’ll keep fighting as we always do.

“As usual, the starts are always one of the most crucial points of the race for us, so getting the set-up just right on Friday in time for qualifying on Saturday will be the most important thing.”

Another troubled weekend would also do little to stem the increasing tension between Honda and McLaren, with speculation of a split only gaining pace.

F1 chief Yusuke Hasegawa insists the factory in Japan remains focused, as they look to solve both the vibrations and some of the reported 90 horsepower deficit with the next significant upgrade of which the parts brought this weekend are the first step towards.

"There will be some kind of improvement in the combustion engine in Baku," he confirmed to Japanese publication Sportiva.

"I don't know if you can call it specification three, but we'll definitely introduce something even if it is intermediate."

Asked what was causing the delay of 'specification three', Hasegawa explained: "If you improve the combustion engine, the temperature of the exhaust decreases by being more efficient, which reduces the energy recovered through the turbo and MGU-H, making it necessary to change these parts too.

"The situation is more complicated than people can imagine."