Aston Martin and Cosworth were among several new parties which sat in on a Power Unit Working Group meeting which took place earlier this week.
An initial working session devoted to F1's future power unit plans and held back in March was attended by representatives of the Volkswagen Group.
This week's meeting was held on Monday in the presence for the first time of representatives from Aston Martin, Cosworth, Magnetti Marelli and Zytek, according to Motorsport.com.
F1's sporting boss Ross Brawn is hard at work designing the sport's post-2020 engine rules and the meetings are likely a means of collecting views from all relevant parties as a foundation is defined.
All participating parties in the process have apparently agreed that F1's future engine format should retain its link with modern-age hybrid technology, albeit within a simplified framework.
A third meeting has tentatively been scheduled for September, before an assembly of the World Motor Sport Council, after which a joint proposal from the FIA and F1 regarding the engine of the future should be formulated.
In the interim, Ross Brawn will continue to meet individually with participants in the process.