"While we're still the U.S. sales leader, we acknowledge we have disappointed you," the company said in Automotive News. "At times we violated your trust by letting our quality fall below industry standards and our designs become lackluster."

The ad containing the letter, titled "GM's Commitment to the American People," appeared as the U.S. House of Representatives on Monday finished drafting a federal aid bill that is less than half of the $34 billion the Big Three automakers sought last week, The Washington Post reported. Executives of GM, Ford Motor Co. and Chrysler LLC testified on Capitol Hill about why they need federal assistance and pledged to turn their businesses around.

"It's addressing what Congress wants to hear but they do realize they've made mistakes," auto industry consultant Laurie Harbour-Felax told the Post.

Saying "I'm sorry" doesn't come easy for corporate America, said Gene Grabowski, chairman of the crisis and litigation practice at Levick Strategic Communications, with offices in Washington, New York and London.

"When you're a publicly held corporation, every utterance you make is scrutinized by Wall Street and has consequences in the marketplace," he said to the newspaper.

But public contrition is only a first step, another observer told the Post.

"Talk is pretty cheap," said Jonathan Cohen, a University of Florida law professor who studies corporate apology-making. "Action is often more telling."