Formula One's new power unit agreement from 2017 is better than nothing but still far from what might have been achieved, according to Red Bull team principal Christian Horner.
While the four major manufacturers welcomed the guarantee of stable rules, and highlighted efforts to reduce costs and performance gaps, Horner sounded a discordant note at the Spanish Grand Prix.
"It's a very soft agreement between the manufacturers and the FIA," he told reporters.
"It tickles the price, deals a little bit with convergence, the obligation to supply doesn't really apply, so it's a very weak agreement.
"Unfortunately it's a shame more couldn't be done, but I suppose if you look on the bright side it's better than nothing."
The sport announced last month a deal to ensure all teams have access to an engine supply, with prices cut over three years and a move to make performance more equal.
The wording of the deal also contains what one team principal dubbed a "Red Bull Clause" that prevents teams and their engine suppliers from publicly denigrating each other.
Red Bull, whose engine now carries Tag Heuer branding, are still supplied by Renault despite a falling out with the French manufacturer last year.
The former champions tried in vain to find an alternative suppplier before patching up a relationship that appeared to have reached a terminal point.
Force India deputy principal Bob Fernley, whose team use Mercedes engines, said he would reserve judgement on the agreement.
Renault, Honda, Mercedes and Ferrari were more positive, however.
"We achieved a major price reduction over two years. We have opened up development scope for others to catch up. We have designed an obligation to supply so no team runs out of an engine contract," said Mercedes motorsport head Toto Wolff.
"We have found a mechanism how performance convergence could be triggered. Lots of good things, many months of hard work in trying to get everybody on the same page, I think it's a good step forward."
Renault F1 managing director Cyril Abiteboul added: "No-one can guarantee performance... but we all know what we have to do. It's good, it's a relief, because we know what we have to do and we can make plans for the future."