Pirelli has admitted the latest changes it made to its compounds are as far as they can go in terms of development for 2013.
Following several complaints over the high degradation levels of its tyres, the Italian company decided to modify its rear rubber for this weekend's Canadian GP.
Teams will be issued two sets of the new specification tyres, which will feature a 2012-style kevlar belt, for Friday practice only at the Circuit Gilles Villeneuve.
Pirelli motorsport director Paul Hembery concedes they have reached their limit in terms of development for this season.
"Ideally we'd like to change the harder compound to give us more guarantees of being under three stops," Hembery is quoted as saying by Press Association Sport. "But you have to understand that sort of change needs the agreement of all 11 teams. It's not something we can do in isolation, and there are reasons for that.
"Teams have taken different design approaches, so some feel they don't wish to be penalised by an in-season change that may alter their performance levels.
"We also get the other comment that drivers can't push, and there are limiting factors. At the end of the day you can only use what you have, not what you don't have.
"Someone once said to me a driver on today's tyres is a bit like asking Usain Bolt to run the 100 metres in high-heeled shoes. In reality, if everybody has to wear the same high-heeled shoes then the competition changes and you use what you have available, not what you don't have available.
"So every team has the same opportunity, and in the end the best car and driver will win the Championship."
There has been a high rate of tyre delamination so far this season, which is one of the main reasons for the changes.
"We have seen a small number of tyres this year with the tread that has come away," Hembery added.
"We've used 12,000, 12,500 tyres this year, and we've seen 14 where we've had images of the tyre getting a cut which goes through to the belt and it creates overheating.
"You then see the dramatic delamination, which visually is not very good, even though the tyre does remain inflated, which is positive.
"But it's an issue that for the general interest of the sport we know we needed to change.
"So we've been working on our inner-drum testing and creating that type of defect by basically putting cuts in tyres.
"That enabled us to come up with a solution which in reality is very close to what we have been using in the past.
"In a sense the belt pack is the 2011-2012 one used by all teams up until last year. We're confident it provides a solution to delamination."