Pirelli is undertaking the final test of its 2020 Formula 1 prototype tyres with Mercedes reserve driver Esteban Ocon at Paul Ricard, as the debate over extra testing continues.
The tyre manufacturer has a two-day "blind" test on Thursday and Friday at the French Grand Prix venue, which represents the last of the 2020 tyre test days.
Pirelli is under pressure to achieve the requirements of the 2020/21 target letter that was circulated last month, and it has requested an extra test to allow it more time.
It has to provide the definitive 2020 tyres for all teams to run at the Abu Dhabi test in December.
At Monza last weekend, the teams failed to come to a unanimous agreement on extra testing.
The matter will be discussed again - along with the contents of the target letter - in a meeting in Geneva on Thursday which will focus mainly on F1's 2021 overhaul.
If Pirelli is unable to schedule an extra October test, there is still an option to run prototype tyres during practice for a grand prix weekend.
But if extra running is not agreed by the teams, the likelihood is that Pirelli's 2020 tyres will end up being much closer to the current versions than had been anticipated.
"We are going to discuss, in Geneva on Thursday, a number of topics related to tyres," Pirelli F1 boss Mario Isola told Autosport.
"I'll be part of the discussion, so we'll explain exactly what we are doing, and what we can achieve, and what we can do.
"At least we have the opportunity to explain what is going on on our side. This week's test in Paul Ricard is fixed, and we are going to continue the development to finalise the 2020 tyres.
"The meeting is September 12th, our test is September 12-13th, so after the meeting, I hope we have an agreement for 2020 tyres, and we will select the best prototypes in the direction of these expectations."
He added: "We started the discussion on targets quite late in the year, and we had already started our development. So if we want to achieve something different, compared to what we have now, we have also to consider an extra test."
The F1 calendar makes an October test difficult because it would take place during the flyaway race schedule.
"We know that Pirelli needs more test time," Renault's Cyril Abiteboul told Autosport. "I think it's important that we need to find a way to do it, to support them, but also in a way that's fair to all competitors.
"It's a bit of a frustrating situation, but right now we need to be able to come together to support Pirelli so that we have a product that is spectacular, safe and appropriate for F1."
At the Paul Ricard test, Ocon will share the track with Sergey Sirotkin as the former Williams F1 driver is testing Pirelli's 2021 prototype 18-inch tyres on a Renault mule car.
This year, three teams are developing mule cars to help with the 18-inch development efforts.
Following Renault's test this week, McLaren will run at Paul Ricard in October while Mercedes will run in December.
Pirelli is still finalising its 2020 F1 compounds but once complete, its focus will switch entirely to the 18-inch development.