MONTREAL, June 6 (Reuters) - Mercedes have delayed the introduction of a power unit upgrade until after this weekend's Canadian Grand Prix due to a "quality issue", the Formula One world champions said on Wednesday.
The decision affects also Williams and Force India as well as the works team.
"All Mercedes-powered cars will be running PU1 (the specification used since the start of the season) for this weekend, too, before receiving new units in France," a team spokesman said.
Mercedes are leading both championships after six races, with Lewis Hamilton 14 points clear of Ferrari's Sebastian Vettel.
Canada is one of Hamilton's favourite circuits, the one where he took his first grand prix win in 2007 and where he has won and started from pole position six times.
If the four times world champion wins again on Sunday he will equal Michael Schumacher's record of seven victories in Montreal.
Renault (PA:RENA), who supply their own team as well as McLaren and Red Bull, and Toro Rosso's partners Honda are planning to bring upgraded power units to Canada.
Mercedes team boss Toto Wolff had said earlier in the week that Mercedes planned to introduce their scheduled power unit in Montreal and were "pushing hard to bring more performance to the car as soon as possible."
Under the 2018 regulations, drivers are only allowed three power units per season.
Mercedes, closest rivals Ferrari (NYSE:RACE) and Red Bull have each won two races so far.