Honda has challenged rival manufacturers to enter IndyCar from 2012 and provide engine competition for the new era of regulations.
The Japanese engine maker will supply power units for the 2012-spec cars, but no other manufacturers have yet come forward to express an interest in joining the series.
"Competition is what we want, it's our DNA," Honda Performance Development president Erik Berkman told AUTOSPORT. "We haven't seen anyone else raise their hand but we are hoping they do. Anyone could compete. What's preventing them from throwing their hats into the ring?"
But Berkman reckons it's already too late to start a program from scratch for the 2012 season.
"If a company is not fairly well along their design process by now, you won't launch a reliable product by the start of 2012," he said. "If a company had a suitable product capable of producing 750 horsepower in another series, then we would already know about it.
"We are operating on the assumption there won't be any competition in 2012 – we have to be prepared to be the sole supplier. If sole supply changes to competition at some point, then we have made some investment for that as well."
IndyCar Series boss Randy Bernard claimed at last week's Mid Ohio round that an American engine supplier is "very, very interested" in joining the series. He is also planning a trip to Europe to meet with more manufacturers.