A leading automotive executive at Robert Bosch GmbH says that the North American diesel market may take decades to come to fruition.

Speaking to Automotive News, Bosch's automotive technology business chief Bernd Bohr warned that initial estimates about the take up of diesel may have to be scaled back.

He had predicted that 20 per cent of North American light vehicles would run on diesel by 2012, but now says that it could take another two years because of weaker than expected consumer demand.

"Obviously, there are a lot of unknowns which go into this - one being the oil price," he explained.

"And it's always difficult to put a forecast on customer sentiment."

He acknowledged that North American consumers had so far proved wary of diesel technology, but forecast that demand would steadily rise as the price of petrol goes up.

Mr Bohr also noted that a number of major manufacturers were developing their own diesel lines ahead of an expected surge in demand.