A U.S. federal judge in Florida postponed the arraignment hearing on Wednesday of a Credit Suisse banker accused of helping wealthy Americans hide their money from U.S. tax authorities.

Christos Bagios, a senior private banker at Credit Suisse, was arrested in January and later charged with helping U.S. clients evade taxes on assets and income while he worked at UBS from 1999 to 2005, according to a criminal complaint.

The court appearance by Bagios, a Greek citizen and Swiss resident, to plead guilty or not guilty to the charges has been repeatedly delayed.

The postponement comes nearly a month after the U.S. Justice Department disclosed that eight offshore banks are the subject of grand jury investigations examining whether they helped Americans evade taxes.

The Justice Department did not identify the banks in making the probes public. But Credit Suisse has said it is under a grand jury investigation.

According to Swiss media reports, the United States is seeking details on all U.S. clients with accounts worth at least $50,000 between 2002 and 2010 at banks including Credit Suisse, Julius Baer and Wegelin as well as the Zurich and Basel cantonal banks.

The disclosure by the Justice Department occurred as several Swiss banks have been in talks to reach a settlement with U.S. authorities over their offshore private banking services.

Those talks have been bogged down in part over issues involving immunity for foreign bankers.

Bagios is accused of helping as many as 150 U.S. clients conceal as much as $500 million from the Internal Revenue Service, according to the criminal complaint. He was released on bond in March.

The complaint said U.S. prosecutors learned about his involvement in tax fraud from Renzo Gadola, one of his bosses at UBS who headed a division that oversaw its undeclared offshore private banking services for wealthy Americans.

Gadola pleaded guilty in December in Miami to helping wealthy American clients evade taxes through hidden Swiss accounts. He is due to be sentenced on November 18.

UBS paid a $780 million fine in 2009 to avoid indictment on charges that it sold banking services enabling rich Americans to evade taxes.

Until his arrest, Bagios was head of Credit Suisse's Relationship Management West Coast group, a private banking unit that is part of Credit Suisse Private Advisors, according to the bank's website.

(Additional reporting by Tom Brown. Writing by Kevin Gray. Editing by Robert MacMillan)

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