The Italian outfit wants to introduce a narrower engine block for next year's power unit, in a bid to help with aerodynamics and lift the overall performance of the car.

There had been suggestions that the team could run the new version as early as the Austin weekend, giving the unit to Kimi Raikkonen so he could begin evaluation of the project over the remainder of the campaign.

However, with next year's engine regulations set to be opened up – after manufacturers agreed to allow 32 development tokens instead of 25 – the urgency to take action now has diminished.

That is why sources have suggested Ferrari is closing to deciding to hold fire on the new power unit for now, although final confirmation of its plans may not come until later this week.

Lorenzo Sassi, the chief designer of Ferrari's power unit, admitted that the team was evaluating several ideas of how best to make use of its remaining development tokens.

"We still have four left and plenty of ideas on how to spend them, both on increasing power for this season and also looking ahead to 2016," he said.