Red Bull's Max Verstappen is likely to suffer a grid penalty at some point this season for exceeding his permitted engine allocation.
Honda has discovered that the power-unit in Verstappen's car when he crashed with Lewis Hamilton at the British Grand Prix cannot be repaired.
Verstappen is already on his third of three allowed engines.
The Dutchman will likely need to use a fourth engine, which would mean a start from the back at a future race.
The situation is a significant blow for Verstappen in his title battle with Hamilton, who leads the championship by eight points ahead of this weekend's Belgian Grand Prix.
His team-mate Sergio Perez is in the same situation following a collision at the start of the Hungarian Grand Prix.
It is not clear how many races remain this season as F1 is still trying to finalise the calendar following the cancellation of the Japanese Grand Prix and amid problems caused by global travel restrictions in the pandemic.
Honda said it was working on the assumption of there being at least another 11 races. This is almost certainly more than can be completed with each Red Bull driver's current engine allocation.
Honda F1 technical director Toyoharu Tanabe said on Thursday: "We lost a power-unit for each driver of Red Bull Racing and it looks like we will have around 22-23 races on the current basis, so we must think our PU strategy accordingly."
The situation means Verstappen and Perez effectively have only one engine to do half the season with, when each power-unit is designed to be able to sustain a mileage equivalent to about a third of the championship.
Both Verstappen and Perez have used their first engine for its full designated mileage over the first third of the season, and now have had their second written off.
After the Silverstone race, Honda's initial investigations of Verstappen's engine suggested it could be re-used.
But after he ran it for the first two days of the weekend in Hungary, the company discovered a crack and needed to change it for the grand prix.
Further investigations at Honda's R&D HQ in Sakura in Japan during the summer break revealed it could not be repaired.