Valtteri Bottas and Nico Hulkenberg are set to start Sunday's Belgian Grand Prix from the back of the grid after taking a complete set of fresh power unit elements for the race weekend at Spa.

Issues earlier in the season left both Bottas and Hulkenberg on the bubble of their power unit element allocation for the season, with both opting to take new parts at Spa.

Mercedes confirmed it was introducing an upgraded power unit at Spa, which, while aiming to offer its drivers increased performance, does trigger a penalty for Bottas, who was on the limit for power unit parts heading into the weekend.

Bottas will start at the back of the grid after taking a new internal combustion engine, turbocharger, MGU-H, MGU-K, energy store and control electronics. Any additional parts he takes between now and the end of the season will trigger further grid penalties.

Renault's Hulkenberg had used the same number of power unit elements as Bottas through the season, meaning he too will start at the back of the grid also taking a complete new set of power unit elements.

Lewis Hamilton, Sebastian Vettel, Sergio Perez, Esteban Ocon, Lance Stroll, Sergey Sirotkin and Stoffel Vandoorne have also taken some new parts for the weekend, but all are within their season allocation, triggering no further penalties at present.

Bottas and Hulkenberg's grid penalties are set to be formally confirmed by the FIA later today.