Roger Penske, founder and head of the second largest US dealer group, hopes to close his bid to buy Saturn from General Motors by the end of September but has not yet found a replacement source of new vehicles.

Penske told Reuters he was also considering extending the Saturn brand outside North America but would focus first on the US market and possibly Canada. The group also owns dealers in the UK and Europe.

Saturn was originally established as an 'import fighter' to compete with the likes of Toyota and Honda and offered 'haggle-free' fixed pricing.

"I think that we're past midfield with GM. There are always issues that you have to deal with, but I think we're progressing well," Penske was quoted as telling analysts.

"We've said that our goal is to close this transaction by the end of September, and we're prepared to do that," he added.

GM is set to supply Penske with Saturn Aura sedans, Vue SUVs and Outlook crossovers vehicles until at least 2011 but he said deals have not been agreed with any replacement suppliers. There have been reports Penske is eyeing Renault-Samsung which already exports both its own models and a crossover built for Renault.

There has been speculation the Penske Automotive Group would be an ideal way for a Chinese automaker to access the tough, far-flung US auto market through a well established and respected national dealer network but previous attempts (eg Chrysler) to launch Chinese vehicles there in volume have faltered.

If the deal with GM goes through, Penske would acquire the rights to the Saturn brand and buy spare parts stock to service the roughly 3.5m vehicles on the road now.

Around 350 current Saturn dealerships in the United States would continue to be independently owned and operated.

Penske plans to set up 'new Saturn' as an independent company, possibly with other investors, would offer contracts to all current outlets.

"We do not expect to buy any of the existing retailers," he said, according to Reuters. "As you know, Saturn has a world-class dealership network and we hope that most of them will join the new company."