McLaren team principal Martin Whitmarsh said it was crucial for the team to agree a new engine deal with a car manufacturer.
The team announced last week it will reunite with former engine supplier Honda in 2015.
“McLaren needs to be supported and teamed in a full works effort with a major automotive manufacturer,” said Whitmarsh at a Vodafone McLaren Mercedes phone-in.
“We’re going to be doing all we can to win races with Mercedes this year and next, but inevitably moving to Honda in 2015 gives us a bedrock of being one of the big teams.
“It ensures that in the long term we have the resources, the correct structure and focus, to be successful.”
Whitmarsh added the switch between engine suppliers, which will come after the first year of F1’s new engine regulations, will be “a tough challenge for the team”.
McLaren and Honda won their first race together in the 1988 Brazilian Grand Prix and their last race together in the 1992 Australian Grand Prix. During that period they amassed 44 wins out of a possible 80, four consecutive constructors’ championship victories and four drivers’ titles won by Ayrton Senna (three) and Alain Prost (one).
Driver Jenson Button will be reunited with Honda having used their engines between 2003 and 2008.