Hiroshi Okuda, the chairman of Toyota and the head of the Japanese Business Federation, has expressed concern that if Ford and General Motors do not solve their current economic problems, foreign carmakers might suffer a backlash from the United States in the form of protectionist practices.

Mr. Okuda was quoted as saying that “nationalistic sentiment” could trigger such protectionist policies.

The director of a Washington, DC, think tank, International Economics, does not see this as a realistic possibility due to the current international nature of the automobile sector, and said that more attention is likely to paid to the yen-to-dollar exchange rate in solving any perceived inequities.

But Mr. Okuda is not comforted by the argument that the presence of Japanese manufacturing facilities in the United States will work against the idea of seeking protectionist policies. Both Ford and GM have said that they are not looking for any benefits in the form of trade restrictions that would put them in a better position than foreign carmakers.

Such restrictions were avoided in the early 1980s only by voluntary cuts in imports by Japanese car manufacturers. Ford and GM together had a 47 percent share of the market in 2004, down from a 65 percent share in 1982.