Red Bull motorsports consultant Dr Helmut Marko has called on Formula 1's commercial rights holders to be more open about its plans for the sport in 2021.
That's when the current technical specifications and Concorde Agreement stipulating how the sport works are set to expire.
Liberty Media has already shared some of its blueprints for future of Formula 1 with teams. But Marko says that it's not enough - and that key figures in the sport are starting to get anxious about the lack of detail.
"We are a little worried," he admitted to Germany's Bild newspaper.
"At the beginning of April they said we would know in four weeks what the regulations are for 2021.
"Then they said 'end of May'. Now it's the end of June," he complained.
"So far we only have statements. It's high time we got concrete data and rules.
"For our future in Formula 1, the new rules must finally be on the table," he insisted.
Asked why he thought things were taking so long, Marko replied: "I think they and Ross Brawn want to please everyone [but] it won't work."
Red Bull has long-standing concerns about engines, believing that the current regulations give too much power in the sport to the manufacturers.
Red Bull is currently supplied with Renault engines. In the past, its attempt to split from the French company was stymied because neither Mercedes nor Ferrari were willing to provide power units to a key rival.
The team is now considering a possible move to Honda for 2019, after a successful start to the season for junior team Toro Rosso which made its own switch to the Japanese manufacturer over the winter.
Asked if he was now feeling any happier about the state of the F1 engine market, Marko was typically forthright.
"No, they still exist," he said. "The rules must be such that any one manufacturer can no longer dominate.
"The situation is different now than a year ago when we were almost without an engine. Now we can choose between two manufacturers."
Marko had previously been concerned that Mercedes and Ferrari were in cahoots and operating a 'duopoly', but it seems he's less worried about that now.
"It drifted apart a bit because of the battery affair," he said, referring to Mercedes complaining to the FIA about Ferrari allegedly getting more energy out of their battery in the race than allowed by the regulations.
"Mercedes above all needs Formula 1 more than the other way around," he added. "They have a different status to Ferrari."
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