Mercedes team principal Toto Wolff says it would be "madness" to push through major changes to Formula One's engine regulations in 2021 as it would require existing manufacturers to develop two power units in tandem.
F1's next engine formula is at the centre of plans to provide closer racing and a more level playing field among teams in 2021.
Earlier this year, F1 proposed a change in regulations that would keep the current V6 engine architecture but remove the complicated MGU-H from the hybrid system. The plan also permitted an increase in the fuel allowance to help the engines rev higher and sound better, while an upgraded MGU-K was tabled to ensure they remained both powerful and road relevant.