Despite a profit warning from Ford last week, billionaire investor Kirk Kerkorian is solidifying his offer to buy more shares of the American car maker.

Tracinda Corp, Kerkorian's investment company, waived a clause that allowed it to back out of the offer to buy 20 million additional shares of Ford stock at $8.50 per share if they fell by more than 10 percent from the close of trading on May 8.

Shares began the day at $6.88, down 18 percent since the initial offer on May 9. After today's Tracinda disclosure, shares rose 5 cents to $6.75 in mid-day trading.

Ford chief executive Alan Mulally said last week that it no longer expected the company to meet its goal of becoming profitable again by 2009.

The company cited the weak economic and environment and a consumer shift to more fuel efficient cars, away from Ford's strengths in trucks and sport utility vehicles.