It had been reported engineers belonging to the Japanese marque, having withdrawn its works team from the sport in 2008, might now already be working at Woking.
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However, it is possible that contract - where McLaren has only 'customer' status - could be superseded by the Woking based team agreeing a 'works' deal.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."