DETROIT (Reuters) -- General Motors today unveiled an unusually frank advertisement acknowledging it had "disappointed" and sometimes even "betrayed" American consumers as it lobbies to clinch the federal aid it needs to stay afloat into next month.

The print advertisement marked a sharp break from GM's public stance of just several weeks ago when it sought to justify its bid for a U.S. government on the grounds that the credit crisis had undermined its business in ways executives could never have foreseen.

It also came as CEO Rick Wagoner, who has led the automaker since 2000, faces new pressure to step aside as GM seeks up to $18 billion in federal funding.

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

The unsigned open letter, entitled "GM's Commitment to the American People" ran in the trade journal Automotive News, which is widely read by industry executives, lobbyists and other insiders.

In the ad, GM admits to other strategic missteps analysts and critics have said hastened its recent decline.

"We have proliferated our brands and dealer network to the point where we lost adequate focus on the core U.S. market," the ad said. "We also biased our product mix toward pick-up trucks and SUVs."

But GM also says in the ad that it was hit by forces beyond its control as it tried to complete a restructuring earlier this year.

"Despite moving quickly to reduce our planned spending by over $20 billion, GM finds itself precariously and frighteningly close to running out of cash," the ad says.

A failure of GM would deepen the current recession and put "millions of job at risk," according to the ad, which also highlights the automaker's pledged restructuring and intention to begin repaying taxpayers in 2011.

GM spokesman Greg Martin said the ad was an attempt by the automaker to present "a pledge directly to the public."

"We believe we need to deliver this commitment unfiltered since quite a bit of media commentary has not kept pace with our actual progress to transform the company," Martin said.

Senate Banking Committee Chairman Christopher Dodd, a Democrat from Connecticut who is central to the effort to craft an auto bailout bill, on Sunday said GM should replace Wagoner.

GM says Wagoner has the support of the company's board.