Cockpit protection may not be introduced in 2017 after all, following the debut of the updated Halo 2 prototype at Silverstone.

Now positioned further forwards to prevent a driver's head from striking the titanium-based structure in a crash, the revised version was given its maiden outing on Friday by Sebastian Vettel.

"My feeling with it was not great," the Ferrari driver is quoted as saying by Brazil's UOL. "I think the impact in terms of visibility is quite a lot."

Indeed, the FIA met with F1 technical bosses on Wednesday at Silverstone and encountered a sceptical atmosphere, according to Germany's Auto Motor und Sport.

One new fear is that in the event of a T-bone style crash, Halo "could act like a guillotine", Force India's Andy Green is quoted as saying.

It is understood that Red Bull's Christian Horner is calling for a strategy group vote on the issue before the summer break, with Auto Motor und Sport believing that a delay until 2018 is currently the most likely outcome.

The German report, meanwhile, added that Halo 3 will now need to be developed.