The FIA is set to release the definitive 2021 Formula 1 engine regulations to manufacturers this week.
While the basic concepts were announced jointly by the FIA and F1 last October, refining the detail in conjunction with the four current suppliers and potential new entrant Porsche has taken months of discussion.
The process was also deliberately relaxed because the FIA had an eye on costs, believing that had full details been issued too early the manufacturers would simply have pumped more resources into beginning development.
It set a self-imposed deadline of the end of June and will now meet this.
"It's very complicated," said FIA F1 race director Charlie Whiting. "There's meeting after meeting after meeting going on these things, and the reports I get on this appear to be very detailed, so they are going into fine detail.
"So I'm fairly confident that it's getting to the end of that process, and at the end of that process, we'll have a far more detailed idea of what the power units will be in 2021."
Whiting denied the end of June deadline was chosen to facilitate discussion by the team bosses at the next Strategy Group meeting on July 4.
"Not necessarily. It was just a date that we felt that was necessary to get it done by," he said.
"It might get talked about, but it's not connected with the Strategy Group.
"The manufacturers are involved in it, that's why it's taking quite a long time because they are to-ing and fro-ing on everything."
But Mercedes motorsport boss Toto Wolff said engines and cost controls would definitely be a Strategy Group topic, with some having suggested a freeze on development of current engines for 2019-2020.
"The engine, it needs a lot of lead time, therefore the earlier the better it is," he said.
"The solution that we need to find is how can we avoid parallel costs of developing two power units.
"Obviously our fight with our friends from Honda, Renault and Ferrari will continue until the very last race of 2020.
"And at the same time, the moment the rules are ratified, everybody needs to work on the other power unit.
"So this is I think one of the key points we need to discuss from July 4."