Cyril Abiteboul says his Renault Formula 1 team's reservations over agreeing to the proposed 2021 rules sign-off deadline extension stem from fears rivals could try to change the regulations' principles.
A provisional set of regulations was circulated to teams last week, and it was due to go to the World Motor Sport Council next Friday.
But all parties acknowledged a lot of refinement was still required and changes were inevitable.
In a meeting in Montreal on Saturday morning FIA president Jean Todt and F1 chief Chase Carey asked the teams if they would agree to an extension of the deadline from June, as specified in the FIA International Sporting Code, to October to allow more work to be done on the regulations.
The unanimous agreement of all 10 teams is required to convince the World Motor Sport Council to allow that to happen, and following the meeting a letter is to be circulated by the FIA for signing.
While nine teams agreed in principle to the change Abiteboul expressed some concerns on Renault's behalf, although he has not ruled out eventually signing the letter.
"Let's be clear, there is more work to be done," he told Autosport.
"There are clear difficulties to reach all the objectives that have been set, because some of the objectives are contradictory - a better show, and a power to weight ratio that will be worse than it is now, for example.
"These things which are the laws of physics, and that's not going to change whether it's now or October. I'm not totally sure that more can be achieved by October.
"Secondly, we knew that there was milestone of end of June for maybe one year, or a year and a half. What have we done?
"We are finally actively working because we are getting close to deadline. It's like a bad student doing his homework the day before the exam.
"I'm just a bit afraid that we'll end up in the same situation, and having the same conversation, in mid-October.
"And finally it's clear that some people are really pursuing changes that are good for the sport, and for sure that we need to make sure that we are doing the right thing for the sport, and not just for Renault, or for Mercedes.
"I completely accept that this takes time, but with the right spirit it can be done, and with the right leadership from the FIA and F1 it can be done, whether or not we push back that milestone.
"But it's also true that there are a number of teams who would prefer that these changes do not happen, so we are just giving more time to the system to find reasons for not doing the changes which we believe are required for the sport - looking at the viewership, looking at the difficulty to attract sponsors, and so on. So that's our concern."
Abiteboul said Renault will agree if it can be assured that creating extra time by not following the established procedures will not allow teams who object to the planned changes to force through a watered down version.
"Our style has been to be progressive about the challenge, so if we presented with the right assurances that the principles will not deviate from the key principle and the key objective, I think we will be constructive," he said.
"It requires unanimity. We need to sign, but everyone needs to sign.
"It was very clear that there was very little being said by some teams, which suggests that some of the teams don't care, which to me is a bit of a concern, because we should all be caring for the process, and the milestones that are coming from the International Sporting Code, and if they're here, they must be here for a reason.
"But again, we will be constructive if the letter is written with the assurance that we are looking for, particularly on the principle and in terms of governance - that we want the FIA and F1 to be able to do the changes that they want.
"I'm not seeking any particular rights, I'm just seeking that no one will have any capacity to block during that time."