Mercedes are just 50 horse power shy of the landmark 1000hp breakthrough with their current F1 'power unit'.
Auto Motor und Sport reports that GPS measurements made by a rival of the German marque's engine output at the end of 2017 showed 949hp.
However, the report claims that Mercedes engine chief Andy Cowell is "confident Mercedes will succeed" in breaking through the 1000hp barrier before the regulations conclude in late 2020.
"If the world champions maintain their approximate development speed, 1000hp will be reached in 2019," the report said.
Ferrari are next in the power rankings with 934hp, followed by 907 for Renault and Honda's 860hp.
Finland's Ilta Sanomat reports that Ferrari are pushing to get an extra 40hp from their engine in 2018, even though engine boss Lorenzo Sassi is moving to Mercedes.
"I don't know who said Sassi is a phenomenon, but I don't remember saying it," Ferrari president Sergio Marchionne told Marca.
"What is true is that our problems were due not only due to him. Our intention was to keep him in GTs, but unfortunately he decided to leave and continue his career elsewhere.
"For the team it's a normal change and now we have Corrado Iotti and we're fine with him."
Finally, Renault's Cyril Abiteboul told Auto Hebdo that he blames former boss Flavio Briatore for the French marque's current power deficit.
"We are still paying the price for Flavio's decision in 2007 to dismiss hundreds of people when engine development was frozen," he said.
The new season gets underway on March 25 with the Australian Grand Prix.
