Formula 1 rejected a proposal to delay the introduction of the 2021 rules revolution until 2022.
Next Thursday is the already-postponed deadline for the publication of the 2021 rules, featuring radically different cars and a budget cap.
But there are fears that, in preparation for 2021 but not restricted at all by the budget cap, big teams may go on a legitimate spending-spree in 2020.
"I think with hindsight we would have been better bringing the cap in first for 2021 and then taking more time to develop these regulations and bring them in for 2022," Red Bull team boss Christian Horner said in Mexico.
He said he is worried 2020 will otherwise be "a very expensive year" that will "create a broader gap" between the big and the smaller teams.
Mercedes team boss Toto Wolff backed Horner's "logical" proposal.
But he said: "It didn't trigger enough appetite with the ones who decide."
Wolff said the FIA and Liberty Media are therefore still on schedule to publish the full 2021 regulations next week.
"I don't think these regulations are going to be stopped. It's been made very clear that this is moving forward," he said.
"There will be tweaks and changes in detail and interpretations but broadly I think this is moving forward."
