Zurich, Jan 19 (Agencies): A Swiss banker who claims to have handed WikiLeaks details of rich tax cheats acknowledged on Wednesday that he made mistakes in his effort to expose the world of offshore tax evasion.

Rudolf Elmer said his nine-year campaign against former employer Bank Julius Baer was marred by missteps, as he awaited sentencing before a Zurich court on charges of coercion and breaking Switzerland's strict bank secrecy laws.

"I made big mistakes, I admit that," he told reporters during a break before the verdict. "I wouldn't say I'm a hero, but also not that I'm a traitor."

Zurich prosecutors allege that Elmer stole client data after being fired from his job at the Cayman Islands branch of Julius Baer, and then tried to extort money from the Swiss-based bank and its senior executives.

Prosecutor Alexandra Bergmann also alleges that Elmer, 55, illegally gave details on the bank's offshore clients to tax authorities, media and later WikiLeaks.

Elmer claims he was being persecuted by the bank.

"I was in an extreme situation," he said. "It's logical that I developed a defense strategy."

Elmer said he was also trying to expose a widespread system of tax evasion by rich businesspeople and politicians.

The case has generated intense interest abroad because of the link to WikiLeaks, and in Switzerland, where bank client privacy has a special place in the national psyche.

Several Swiss banks including UBS AG and Credit Suisse Group have suffered embarrassing data leaks in recent years, some at the hands of disgruntled employees.

Appearing before a single judge at Zurich's administrative court today, Elmer admitted sending threatening messages to some bank officials, but insisted he had done so after the bank fired him from his job as chief operating office on the Cayman Islands and then intimidated him.

He denied issuing a bomb threat against the bank, but admitted threatening to send details on its exclusive offshore clients to tax authorities in Switzerland, Britain and the United States. Elmer said the data would also be sent to Neo-Nazi groups "and other organizations which fight the capitalism (sic)," according to a prosecution statement.

Prosecutors say authorities have launched at least one tax evasion case after receiving the data.

The prosecution case against Elmer, who claims to have suffered physical and psychological illness as a result of his treatment by the bank, reads like a mix of farce and Jason Bourne novel.

Elmer was fired in 2002 after refusing to take a lie detector test on the Cayman Islands, where he had worked for the bank for eight years.

Prosecutors claim he spent the next few years moving between Switzerland, the Isle of Man, Germany, Austria and Mauritius. At times he is alleged to have offered to sell stolen data back to Julius Baer, at times he threatened to expose what he described as "unethical or even criminal behaviour" by the bank's senior management.