F1 manufacturers have failed with planning rules - Christian Horner

Mercedes, Ferrari, Renault and Honda have until the end of this month to finalise a plan for the FIA regarding price reduction, guarantee of supply, noise levels and performance convergence - a deadline Horner does not expect to be met.

Horner has pointed an accusing finger at Mercedes chief Toto Wolff, in particular, given his role as 'head' of the committee of the engine manufacturers charged with drawing up the plans.

"He knows he's failed to achieve any of the criteria with what he was tasked with doing," Horner said.

"Obviously there's been an element of stalling and playing for time for the date [the April 30 deadline] to naturally lapse.

"What the manufacturers are looking for is a quid pro quo - looking for stability of the regulations for the next five years, which I don't believe the commercial rights holder or governing body will do without the criteria having been met.

"If they're now not available - if prices aren't going to come down, convergence isn't going to happen, supply isn't going to be [guaranteed] - then the criteria hasn't been fulfilled."

Horner believes if no agreement is reached at the next Strategy Group and F1 Commission meetings FIA president Jean Todt and supremo Bernie Ecclestone will again push for an independent engine.

"How else are you going to deal with price, availability and convergence?" he added. "It's still a major, major issue.

"The racing is good at the moment, but we've still got this underlying issue that needs to be addressed.

"It's going to be interesting. It's not something that's going to be finished in a week."

Wolff, however, is adamant Mercedes and the other three engine manufacturers are close to reaching a conclusion.

"We are pretty much there," said Wolff.

"We have an agreement that needs to be ratified by the stakeholders, and there are a lot of benefits for most of the teams so I am hopeful that will be done."

Wolff was supported by McLaren racing director Eric Boullier who said: "There is nothing drafted yet, but there was a good debate [in a meeting in Paris on April 18].

"Christian was not happy in the meeting, so he is voicing his unhappiness, but there has been progress at least between Honda, Renault, Ferrari and Mercedes.

"Nothing is drafted, signed or agreed, but the discussion was positive and constructive."