Spain and Hungary are understood to have been chosen as the venues to hold the two-day in-season tests for next season.
Subject to contracts being finalised, the Circuit de Catalunya-Barcelona and the Hungaroring have been chosen by the teams to host both in-season tests.
In-season testing returned in 2012, sporting regulations mean such tests are allowed to take place but, under strict rules, must take place at circuits that have just hosted a grand prix.
Teams must also field a young driver in two of the four days across the year, this allows test and reserve drivers to have a chance to test F1 machinery.
The tests will take place on the Tuesday and Wednesday after each grand prix weekend; the Spanish Grand Prix has been pencilled in on the provisional 2018 calendar as mid-May, with Hungary keeping hold of its late July slot.
The return of the French Grand Prix at the Paul Ricard circuit next year saw one team try to push through a potential test at the track but other outfits did not back this request.
As well as in-season tests, teams will also be permitted to helping Formula 1’s tyre supplier Pirelli improve the design of its tyres in dedicated tyre testing.
