Plans for a fifth engine in Formula 1 this season are to be ditched, claims Mercedes chief Niki Lauda, with the idea having failed to get the unanimous support it needed to come into force.
As Motorsport.com reported in March, teams had backed the idea of allowing an extra power unit to be used in 2015 as a way of ensuring plenty of running in Friday practice sessions.
But as the implications of the rule change became clearer, and some teams wanted the extra engine for competitive benefits, resistance to the switch emerged.
Now, ahead of a meeting of F1's Strategy Group on May 14, Lauda thinks that the rule change will get vetoed, ensuring that all drivers remain limited to four engines.
"There will be no fifth engine," Lauda told Austrian news agency APA. "You cannot change the regulations in the middle of a season."
Motorsport.com understands that a key factor in deciding on the engine will be whether or not the extra power unit is used for more Friday running.
The failure to allow the extra unit will be a particular blow to Red Bull, after its run of engine failures this year.
Daniel Ricciardo will already be on his fourth and final engine for this weekend's Spanish Grand Prix, meaning it is inevitable he will get power unit penalties at some point this campaign.
Red Bull team boss Christian Horner said last month the planned fifth engine rule tweak had been agreed by everyone when it first came up.
"We unanimously agreed on it in Malaysia," Horner said.
"That was all the teams, including Bernie Ecclestone, so it only has to formally go through the Strategy Group and permission to be signed, and that can be done by fax vote."