F1 engine suppliers Ferrari and Renault appear to have won a battle in the long-running 'freeze' saga.
Mercedes' struggling V6-making rivals have been pushing hard for changes to the existing homologation rules, where performance improvements of the 'power units' is tightly restricted during the season.
The next 'freeze' deadline was believed to be February 28, where all four 2015 makers - Ferrari, Renault, Mercedes and Honda - must present their engines to be homologated by the FIA.
But Ferrari and Renault had reportedly argued that a loophole existed in the rules, where they could start 2015 with last year's engine and then introduce improved new power units at a later date during the season.
The BBC reports that the matter was discussed at last week's Strategy Group meeting in Geneva, and "it now seems likely that manufacturers will be able to upgrade their engines after the start of the season as well as before it".
Germany's specialist Auto Motor und Sport is reporting similarly, claiming that any engine maker "who does not use all 32 (development) tokens by February 28 can continue to make progress during the season".
Roger Benoit, a veteran F1 correspondent, wrote in the Swiss newspaper Blick that the 'freeze' saga is "so sensitive that Mercedes and Honda have already threatened to quit".
'Selfish' Red Bull
Outspoken 1997 world champion Jacques Villeneuve, however, does not buy into Red Bull chief Christian Horner's argument that the engine rules need to be urgently changed altogether.
"He's saying that just because they don't have a Mercedes engine," he told Italy's Omnicorse. "Otherwise he wouldn't want to change the rules.
"He's not thinking about the good of Formula One, but only his team and his future," Villeneuve charged.