Formula 1 is nowhere near meeting the FIA's 2017 engine regulation criteria and is unlikely to find a solution before the April 30 deadline, says Red Bull boss Christian Horner.
Teams have been tasked with agreeing a new set of aerodynamic and engine rules for 2017, with FIA president Jean Todt expressing confidence earlier this month that the looming deadline would be met.
But while the aerodynamic changes are close to being finalised, it seems there is some way to go to find a way forward with the cost, performance, noise and supply of power units.
"It's a complex situation but fundamentally, there were four criteria that were requested by the governing body to be met to ensure stability moving forward," said Horner.
"Those four criteria were a significant reduction in cost to 12million euros, the availability or guarantee of supply, power convergence to within a relatively small bandwidth and to address the noise.
"As we sit here now, we're not anywhere near having met any of those criteria.
"Unfortunately what will happen, as is often the case with these things, is time will run out at the end of the month and nothing will be achieved and nothing will change.
"There is one more attempt in the Strategy Group meeting and F1 Commission meeting at the end of this month to discuss the concerns and where we are at but failing that, the regulations will inevitably stay as they are."
Mercedes boss Toto Wolff agreed with Horner that it was a complex scenario but insisted a solution must be found in time.
"It is a complex agreement," he said. "We have been given the task in coming up with solutions so no team is left without an engine.
"All manufacturers have acknowledged that.
"There is an aspect of price reduction which is important to most of the teams.
"We tried to cover that in a framework agreement.
"It is difficult to make everyone happy. Christian isn't so happy.
"But we need to come up with a solution by 30 April.
"At the moment, everyone is working hard to find the smallest common denominator."
Regarding the aero regulations, Horner said they have been "basically agreed" and the teams "are already tentatively looking to next year based on those regulations".
He added: "They are interesting rules, they add an element of variance compared to what we currently have so you will see some different solutions from different teams than you usually get when there is a regulation change such as that."
McLaren racing director Eric Boullier added: "It's exciting to have a new package.
"The cars will be faster and drivers will enjoy driving the cars. If the drivers are happier, fans are happier I guess."