By Alan Baldwin
LONDON (Reuters) - Formula One's four manufacturers have agreed a deal to reduce the cost of engines and ensure that no team is left without a supply, sources at the governing FIA said on Tuesday after meetings in Geneva.
In exchange, the manufacturers were assured that the current V6 turbo hybrid power unit regulations would remain stable until at least 2020, staving off the threat of an alternative independent supplier being introduced.
The sport's core Strategy Group, which includes the six top teams and governing body and commercial rights holder, had met in Geneva on Monday before a meeting of the broader Formula One Commission on Tuesday.
The agreement, details of which had yet to be finalised, will come into force in 2018.
The four manufacturers -- Ferrari, Mercedes, Renault and Honda -- had agreed to come up with proposals by last Friday with the FIA and commercial rights holder Bernie Ecclestone threatening to tender for an independent option if no progress was made.
FIA president Jean Todt had told reporters in Birmingham, England, last Friday that he was optimistic a solution was close.
The situation came to a head last year when former champions Red Bull struggled to secure an engine for this season.
In the end they managed to patch up frayed relations with Renault and continue with the French manufacturer after Mercedes ruled out a supply, Ferrari offered only an old engine and Honda's interest was vetoed by partners McLaren.
(Reporting by Alan Baldwin, editing by Toby Davis)