DETROIT -- A top aide to billionaire investor Kirk Kerkorian says Ford Motor Co. should sell its Volvo and Mercury brands.

Jerry York told the Automotive News for a story yesterday he saw no reason for keeping them. York says he's confident in Ford's turnaround plan and thinks the automaker will put Volvo on the market within 18 months.

Kerkorian disclosed Monday that he acquired a 4.7 percent stake in Ford and hoped to boost his holdings. His investment company plans to make an offer for up to 20 million additional shares at $8.50 a share.

Ford spokesman Mark Truby told The Associated Press today that Volvo isn't for sale and that the company is investing in Mercury. But he said the automaker continues to evaluate its portfolio.