BERLIN (Reuters) - A German prosecutor rejected criticism on Wednesday that suspected Nazi death camp guard John Demjanjuk is not being brought to trial fast enough before the 88-year-old dies.

Munich state prosecutor Anton Winkler said his office has been examining evidence against Demjanjuk since December 30, 2008 and hopes to have him extradited from the United States for a trial in Germany as soon as possible -- possibly in the next month.

"We're working as fast as possible and assume Demjanjuk will be brought to trail here," Winkler told Reuters. "As soon as we have finished preparing the charges, the extradition process will move forward."

In November, Germany's chief Nazi war crimes investigator in Ludwigsburg, Kurt Schrimm, asked prosecutors in Munich, where Demjanjuk once lived before he emigrated to the United States, to charge him with involvement in the murder of 29,000 Jews.

Schrimm said his office had evidence that Demjanjuk had been a guard at the Sobibor death camp in Poland and personally led Jews to the gas chambers there in 1943. Last week Schrimm criticized the Munich prosecutors for not moving faster.

"The accusation is unfair," Winkler said, adding that a final report should be ready in about three weeks.

Winkler said charges could be raised at that point and a request for his extradition made to the Berlin government.

Efraim Zuroff, a Nazi hunter at the Simon Wiesenthal Center and director of its Jerusalem office, said time was running out to prosecute Demjanjuk, second on its list of top war criminals.

"The evidence has all been checked time and again," Zuroff said in a telephone interview from Jerusalem.

"It's strange to claim a month's delay is needed. The biggest problem prosecuting war crimes all over the world now is a lack of political will."

Winkler rejected that criticism.

"It's not true," he said. "We have prosecuted many Nazi war criminals in Munich and will continue to follow up every lead."

Ukraine-born Demjanjuk denies any involvement in war crimes. He said he was in the Soviet army and a prisoner of war in 1942. He later went to the United States, working in the car industry.

Stripped of his U.S. citizenship after he was accused in the 1970s of being "Ivan the Terrible," a guard at the Treblinka death camp, Demjanjuk was first extradited to Israel in 1986.

He was sentenced to death in 1988 after Holocaust survivors identified him as a guard at Treblinka. But the Israeli Supreme Court overturned his conviction when new evidence showed another man was probably the notorious "Ivan."

Demjanjuk returned to his home near Cleveland in 1993 and the United States restored his citizenship in 1998.

But the U.S. Justice Department refiled its case against him in 1999, arguing he had worked for the Nazis as a guard at three other death camps and hid these facts when he immigrated.

He will turn 89 on April 3, said Ed Nishnic, his ex son-in-law, who added that Demjanjuk was in poor health.

"He is ill, he's in no condition to go through another trial," Nishnic told Reuters. "He's not able to go anywhere. He is oblivious to it. He doesn't know what is going on."

"I think they have at best a flimsy case and they're walking on very thin ice if they try to bring Mr. Demjanjuk to Germany."

(Additional reporting by Andrea Hopkins in Cincinnati; editing by Michael Roddy)