Mercedes, Ferrari, Honda and Renault are to hold a meeting with the FIA on Thursday to discuss a potential overhaul of Formula 1's engine rules, Motorsport.com can reveal.
Amid concerns that development restrictions and homologation deadlines are freezing in performance advantages too much, the sport's manufacturers have been called to discuss shaking things up to help make a more level playing field in the sport.
It is understood that teams bosses and senior engine representatives from all four of F1's car makers will be in attendance in a get-together that could have big ramifications for the competitive order in 2016 and beyond.
For if there is scope to allow Renault and Honda to make the gains they need to make a big leap forward in performance over the winter, then it could have an impact on Red Bull's engine plans.
One of the key issues at the moment is that a loophole in F1's engine regulations that allowed teams to conduct in-season development this year has been closed off for 2016.
That means all the manufacturers will have to lock down their engine designs for next season by February 28 – which is currently just a few days after 2016's first test has taken place.
Honda, Renault and Ferrari are eager for the rules to be freed up, either by allowing restricted in-season updates or even ditching development restrictions altogether.
While Mercedes could stand firm and block any changes to the rules to ensure it maintains its advantage, Motorsport.com understands it is open to a situation that would allow its rivals to catch up to a limited extent.
It is well aware that locking in the significant advantage it has over Renault and Honda at the moment is not good for F1, and that the sport overall would benefit from closer battles at the front.
However, Mercedes has to be careful in allowing too much freedom for its rivals, because there is a danger that closest contender Ferrari would utilise any update avenues to lift itself to the top of the order.
That is why there are some proposals being put forward to impose limits on dyno testing to prevent manufacturers' costs getting out of control.
Motorsport.com understands that other areas of debate will be over some specific design limits of development restrictions.
Under Appendix 4 of the current F1 Technical Regulations, several areas of engine development have been blocked off totally from any development – even if manufacturers wanted to exploit them.
These 'black box' areas include for 2016 upper/lower crankcase, valve drive, cover, the air valve system and ancillaries drive.
Further restrictions come on board for 2017 and beyond, meaning that the scope for development gets less and less as time goes on.
One idea being discussed is to remove the black box restrictions totally, so that manufacturers can choose any area they want to make improvements.
Any agreements reached by the engine manufacturers for 2016's engine rules will need to be unanimous if they are to go forward to the F1 Commission, where again all teams will need to approve them.
It is unclear how easy it will be to find a consensus though, because talks to allow in-season development collapsed last year, forcing Ferrari to exploit a loophole in the rule to allow the token system for 2015.
The engine makers may also discuss the potential idea of a cost-cap to offer cheaper engines to customer teams - as has been proposed for discussion by the Strategy Group.