Toro Rosso team principal Franz Tost has accused Formula 1's engine manufacturers of stalling for time with regard to the introduction of future power unit regulations.
FIA president Jean Todt and F1 supremo Bernie Ecclestone threatened the introduction of an independent engine unless Mercedes, Ferrari, Renault and Honda came up with suitable proposals to address costs, supply, performance and noise.
Proposals for a €12million per annum cost cap on supplies to customers, guarantees of engines for the full field and 2018-20 rules stability were made by the January deadline.
But talks over the details remain ongoing, and asked whether anything had changed in the two months since the announcement, Tost replied: "They play it quite clever.
"They play the time card, and the longer we discuss, the less solutions we will come up with."
Tost is adamant the manufacturers should bear the brunt of the costs given the relevance of the power unit to road-car technology.
"This is something I addressed four years ago, when the new regulation came in, that costs would increase by a minimum 100 per cent," said Tost.
"People in those days didn't believe it, but it's simply the case.
"And what we missed in those days was saying, 'OK, if manufacturers are in Formula 1, if they come up with this new technology, which is technology for the future, then they should also pay for the possibility to present something all over the world, as a marketing tool'.
"They should pay for this, not the private teams. Now, it's the case that the private teams are covered with very high costs and this is not the correct way.
"Of course it costs some money, but it's a difference of whether you pay, I don't know, 25 million or 10 or 12 million, for a private team."
Tost is hoping a solution will ultimately be found, adding: "This is what the FIA and Formula 1 has to work out, to find a compromise.
"I hope we will find a compromise because for us, the private teams, it is quite difficult to find all of this additional money. That's the financial side.
"On the performance side, the manufacturers are in a position to say, first of all, who gets an engine, and second, they also can more or less decide how good the engine performs. I don't think this is the best way."
Toro Rosso will use year-old Ferrari engines in 2016 after parent company Red Bull attempted to sever ties with its erstwhile works partner Renault.