Both Toro Rosso drivers will take grid penalties this weekend as Honda introduces its latest upgrade.

The move, which will likely see Pierre Gasly and Brendon Hartley start from the back of the Sochi grid, means that the Honda-powered duo don't face penalties for the Japanese manufacturer's home race in just over a weeks' time at Suzuka.

News of the upgrade, which Honda has been seeking to introduce for some time, came via social media, as the Japanese manufacturer tweeted: "We are introducing some power unit updates on both cars here in Sochi.

"We're looking at more performance in the long term, which does mean penalties here in the short term," it added.

Confirming the move, Gasly told reporters: "We need to wait and see exactly all the positives from it, but we will have something, some insight. We will surely start from the back of the grid, it's been a while since we had an update so it's all positive.

"Honestly it is not precise yet," he added, "it's just an update on the engine side. I don't want to say too much before we see on track tomorrow what it will do exactly. It's an update so it should be positive."

Looking ahead to next season when it will partner Red Bull, Honda has admitted that the final races of this season could see the Toro Rosso pair face further penalties as the Japanese manufacturer 'experiments'.

The penalties come at a time sister team Red Bull is also expecting to be demoted as Daniel Ricciardo and Max Verstappen add a further B-spec power unit to their respective pools to see them through the remainder of the season, Renault concerned that the C-spec unit is not ready for the high altitude of Mexico City.

The full number of grid places the Toro Rosso pair will drop will not be known until it becomes clear how many components have been replaced.

Check out our Thursday gallery from Sochi, here.