U.S. — Billy Graham, America's dean of Christian evangelists, has compared the United States to Sodom and Gomorrah, the Biblical cities synonymous with sin.

"Self-centered indulgence, pride, and a lack of shame over sin are now emblems of the American lifestyle," Graham writes in the open letter released by his organization this week.

He blasts what he sees as efforts to keep references to Jesus out of the public sphere.

"Our society strives to avoid any possibility of offending anyone -- except God. Yet the farther we get from God, the more the world spirals out of control," he writes in the letter released Tuesday.

Graham, 93, has preached to untold millions over six decades, and provided counsel to generations of U.S. presidents.

His letter also contains a fundraising appeal and a notice that Graham's son Franklin, himself a major evangelical figure, is launching a new effort to "bring the Gospel into neighborhoods and homes in every corner of America next year."

Randall Balmer, the chair of the religion department at Dartmouth College, suspects the motivation for the letter is at least partly political.

"It's hard for me to believe that this letter does not have political intent," he said.

Its move to decry what he would see as moral decay "would be tied to the Obama administration," he argued, asking rhetorically why Graham would not have issued the statement in response to an event like the Abu Ghraib torture scandal.

Graham's spokesman did not immediately respond to a question about what prompted the letter.

It does not clearly refer to specific recent events.

Balmer said that evangelicals would take note of the letter, though Graham has largely retired from the public eye in recent years.

"There is certainly admiration for Billy Graham, as there should be," Balmer said. "There is lingering respect for Billy Graham and I think that people will take notice."

But he said the comparison to Sodom and Gomorrah -- which Graham attributes to his late wife Ruth in the letter -- was startling.

"When Billy Graham came to Madison Square Garden in 1957, he made comments comparing New York City to Sodom and Gomorrah and was roundly criticized for it," Balmer said. Since that time, Balmer said, Graham has largely avoided making the comparison to the Biblical cities.