Almost every team in pitlane is now opposed to the plan to speed up the cars with more downforce in 2017.

Although designers are already turning their minds to what are expected to be vastly different regulations next year, Auto Motor und Sport revealed on Friday that eight of the 11 teams are actually opposed.

An April 30 deadline has been set for finalisation of the new rules, to feature wider cars and tyres and bigger diffusers and wings for a laptime boost of several seconds.

However, it was reported this week that there is now some uncertainty, and not just because of the delay in the release of wind tunnel tyres by Pirelli, who are yet to sign an actual contract for 2017 and beyond with the governing FIA.

It was believed that Mercedes, Williams and Force India had backed views shared by the likes of world champion Lewis Hamilton, who thinks that more downforce is not the answer to F1's problems.

"If we commit ourselves to wider cars," a source warned, "there is no turning back like with the qualifying format."

Another source told Auto Motor und Sport in Bahrain: "Eight of the 11 teams are now opposed to the introduction of the new car."

One of the three teams still in favour is McLaren, who came up with the blueprint for the 2017 car concept. The other two are Red Bull and Toro Rosso, with Red Bull's Adrian Newey always relishing a new set of aero rules.

However, even with the majority of teams opposed, the 2017 rules could still go through.

"With their voices in the strategy group, Bernie Ecclestone and the FIA could theoretically stop a move in this direction," Mercedes boss Toto Wolff said.

The 2016 calendar continues with the Bahrain Grand Prix this weekend.