DETROIT — Ford Motor Co. (F) said Friday that Robert Rubin, a director at financial services company Citigroup Inc. (C), resigned from the auto maker’s board of directors over a potential conflict of interest that could arise as Ford restructures the business.

In a letter to Ford Chief Executive Bill Ford, portions of which were released to the media, Mr. Rubin said Citigroup’s “multi-faceted relationship with Ford could raise a question whether my relationship with Ford and Citigroup creates an appearance of conflict.”

Mr. Rubin, who is the third board member to leave this year, noted that no conflict of interest currently exists and said he regretted leaving Ford. He has served as a board member since 2000.

Bill Ford is currently leading an internal strategic review of Ford’s various assets, and the auto maker may choose to sell certain units, including European luxury brands or a stake in Ford Motor Credit.Citigroup could potentially play a role in any such effort, Ford spokesman Oscar Suris said in an interview. “The work we plan to do is evaluating all of our strategic options and Citigroup’s potential role could lead to conflicts of interest,” Mr. Suris said. Mr. Rubin “wants to take that off the table.”

Mr. Suris declined to comment on specifics related to the strategic review.

Reports in recent days have pointed to several possible options for Ford. In the latest news Friday, a source familiar with the situation said JP Morgan Chase & Co.’s (JPM) private equity arm, One Equity Partners, is in talks with Ford to acquire some of the auto maker’s luxury brands.The negotiations are still in an early stage and spearheading the negotiations is Jacques Nasser, a One Equity partner who was formerly Ford’s president and chief executive.

Shares of Ford were up 3% at $7.99 in recent trading on the New York Stock Exchange. The stock is up 32% since hitting a 52-week low of $6.06 on July 21, one day after the auto maker said it would accelerate its North American restructuring effort. The recent reports about potential asset sales and alliances have added fuel to the rally.

The loss of Mr. Rubin, who served as U.S.Treasury Secretary in the Clinton administration from 1995 to 1999,is a particular blow to the auto maker because he is widely considered one of the most constructive and experienced directors of the company. “I think it’s a great loss because he’s as strong of a director Ford has in the boardroom,” said John Casesa, president of Casesa Strategic Advisors.

Mr. Rubin’s departure comes amid speculation that tension is growing between the Ford family, which controls 40% of Ford voting interest, and the board. In April, former executives Jim Padilla and Carl E. Reichardt resigned from the board.

Mr. Rubin’s departure leaves 11 board members at Ford, including Bill Ford, who serves as chairman.William Clay Ford Sr, Bill Ford’s father, is director emeritus.

Ford isn’t the only troubled auto maker to lose a critical board member due to potential conflict of interest.In February, Stanley O’Neal, chief executive officer of Merrill Lynch & Co., Inc., left General Motors Corp.’s board of directors, citing demands on his time and potential conflicts related to GM’s restructuring activities.

In January, Ford announced that it would close 14 plants and shed 30,000 jobs as part of its ‘Way Forward’ restructuring plan. However, after a disappointing performance in the first half of the year, the company said it would move faster in its restructuring and would announce its revised plans in September.

On Sept. 14, the board will convene to discuss various accelerated restructuring options that management is considering. The company is considering cutting between 10% and 30% of its white-collar costs.Ford also recently hired seasoned advisors to assist in efforts to potentially overhaul the global organization. Earlier this month, Ford hired Goldman Sachs’ Kenneth Leet to help lead the strategic review.

Bill Ford has said the company is considering all possible options as it carries out its review. In an interview with BusinessWeek magazine published this week, he said the auto maker is considering “radical changes.”

The auto maker is struggling to remake itself following a series of stalled recovery efforts during the five years Bill Ford has been at the helm. In the first half of 2006, Fordbled more than $1 billion in its North American automotive operations, and last week announced a drastic 21% fourth-quarter production cut that promises to lead to more red ink.