CNN

WASHINGTON (CNN) – Best-selling author Jon Krakauer sharply criticized Gen. Stanley McChrystal for his handling of former NFL player-turned Army Ranger Pat Tillman's death, in an interview with CNN scheduled to air Saturday.

Tillman was killed by friendly fire while serving in Afghanistan. Krakauer, author of "Where Men Win Glory: The Odyssey of Pat Tillman," said that despite seeing reports describing the real cause of Tillman's death, McChrystal signed paperwork to award him a Silver Star, which is not normally given to victims of friendly fire.

"I think he has a serious blemish on his record," Krakauer said.

When asked by CNN's Wolf Blitzer if he thought McChrystal should be in charge of U.S. Forces in Afghanistan, Krakauer answered, "No."

"If a lesser officer did what McChrystal did, he would be court marshaled according to Article 107 of the Uniform Code of Military Justice, submitting a false official statement," Krakauer said. "It's a very serious offense for which you, if you're found guilty, you can be dishonorably discharged and you can be locked up for five years."

McChrystal, now the commander of U.S. and NATO forces in Afghanistan, told Congress during his confirmation hearing in June that he made a mistake and misread the report about Tillman's cause of death. But Krakauer said his explanation was "purged. It's not believable. It's preposterous."

"Someone who is guilty of that kind of offense, and I believe McChrystal is, should not be commander of the forces," Krakauer said. "It sends a terrible message. I mean, Afghanistan is fighting corruption… And here's a guy, who five years ago lied to the Senate. He lied to Army investigators. And he submitted this fraudulent document."

But a Pentagon spokesman said McChrystal still believes that Tillman deserves the Silver Star medal.

"General McChrystal acknowledges that in the aftermath of this confusing and emotionally-charged incident he did not review the award citation carefully enough before forwarding it up the chain of command, but to this day he steadfastly believes Corporal Tillman's actions before his death warrant the honor," Pentagon spokesman Geoff Morrell said in a statement.

Tune into The Situation Room on Saturday beginning at 6 p.m. ET for Wolf Blitzer's full interview with Krakauer.