The FIA is conducting one last set of tests on the Halo device this week ahead of a final decision in mid July on its introduction for 2017.
The Halo device is designed to offer increased head protection from large flying objects such as tyres and was chosen as the preferred form of cockpit protection over Red Bull's Aeroscreen.
"There is still a lot of work to make it happen," Laurent Mekies, General Manager Research for the FIA's Global Institute, told ESPN. "We still have testing going on, we still have meetings with the teams coming up and there is the implication for the chassis designs. So there are deadlines we cannot move forever and therefore it is still on a high-pace development right now."
Asked for an exact deadline, Mekies said: "We will not go after July 15. We have the final tests [this week] and we will meet with the teams again early in July and look at the results.
"After that there are implications for chassis design and you will be eating into the time where some teams start to freeze their chassis design, so we don't want to run into that."
Mekies said the final shape of Halo had slightly evolved since Ferrari ran a prototype version during testing, but ultimately the design looks similar to the version tested by Kimi Raikkonen and Sebastian Vettel.
"From a general shape point of view it is close, but the geometry is a bit different because it's a result of the work we have been doing between Barcelona and now. But that is the general concept."
Development of the Aeroscreen has been frozen to concentrate all efforts on Halo for 2017, but Mekies says the Red Bull design has not been ruled out for 2018.
"I think the freezing of the Aeroscreen is only as far as 2017 is concerned because you have to meet a deadline and if we kept on with two projects we would have struggled to do so. At some stage you have to estimate whether or not you are going to be able to make it and it was estimated that we couldn't make it with the Aeroscreen, which is why we froze that part until we get the Halo on the right path for 2017.
"But once this is done, I'm sure everybody, Red Bull and the teams, will continue with the great contributions they have made. Nothing is dead forever, it is only a pure project planning choice in order to make one of the two solutions to the grid for 2017."