Shepard Fairey, the artist whose "Hope" poster of Barack Obama became an iconic emblem of the presidential campaign, has admitted that he lied about which photograph from The Associated Press he used as his source, and that he then covered up evidence to conceal his lie.

Mr. Fairey's admission, which he made public Friday, threw his legal battle with the news agency into disarray.

The AP claimed in January that Mr. Fairey owed it credit and compensation for using the photograph. But in February Mr. Fairey sued the AP, seeking a declaratory judgment that the poster did not infringe on the agency's copyrights and that he was entitled to the image under the "fair use" exception of the copyright law. The AP countersued in March, saying Mr. Fairey had misappropriated the photograph.

Mr. Fairey told the agency -- and his own lawyers -- that he had used a photograph from an April 27, 2006, event about Darfur at the National Press Club in Washington where Mr. Obama was seated next to the actor George Clooney. Instead, the photograph he used was from the same event, but was a solo image of Mr. Obama's head, tilted in intense concentration.

Mr. Fairey admitted that in the initial months after the suit and countersuit were filed, he destroyed evidence and created false documents to cover up the real source. He said he had initially believed that the AP was wrong about which photo he used, but later realized the agency was right.

In Pittsburgh last night, Mr. Fairey addressed the issue, saying it had been weighing on him. He appeared at The Andy Warhol Museum on the North Side for the opening of "Shepard Fairey: Supply and Demand," an exhibition of his work that included a version of the "Hope" poster.

"I'm very disappointed with myself over this," he said during an hour-long question-and-answer session about his career and influences.

While he said he couldn't comment much on the case, he described the issue as a mistake.

"There are some things being portrayed as if I was premeditative and sinister about which photo I used," he said. "That's not the case."

He declined to comment further after his talk.

Mr. Fairey's lawyers said they intended to withdraw when he could find new counsel.

Srinandan R. Kasi, the AP's general counsel, released a statement Friday that said: "Fairey's lies about which photo was the source image were discovered after the AP had spent months asking Fairey's counsel for documents regarding the creation of the posters, including copies of any source images that Fairey used."

Mr. Kasi said: "The AP intends to vigorously pursue its countersuit alleging that Fairey willfully infringed the AP's copyright in the close-up photo of then-Sen. Obama by using it without permission to create the Hope and Progress posters and related products, including T-shirts and sweatshirts that have led to substantial revenue."

A request for additional comment from Mr. Kasi was not immediately answered.

Complicating the legal battle, the freelance photographer who took the photographs, Mannie Garcia, filed court papers in July saying he owned the copyright of the 2006 photograph.

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.