The reports said Honda could possibly be ready with a turbo V6 next year, but that a new one-year deal between McLaren and Mercedes for 2014 is the most likely option before a change of tack in 2015.
Mercedes' Toto Wolff told the BBC: "We are looking for a long term engine supplier relationship with McLaren-Mercedes."
In fact, McLaren and Mercedes already have a contract beyond 2013.
Asked about the burgeoning Honda rumours, team boss Whitmarsh told Britain's Sky: "What I can tell you is we have a contract with a long standing partner, Mercedes-Benz, for 2013, 2014 and 2015."
However, it is possible that contract - where McLaren has only 'customer' status - could be superseded by the Woking based team agreeing a 'works' deal.
Whitmarsh added: "There's a lot of speculation and I've heard Porsche, Hyundai, Honda, all those sorts of names.
"I hope for formula one that these manufacturers come back -- we need them in the sport.
"In the longer term, who knows what's going to happen."