Former high-ranking UBS bank executive Raoul Weil goes to trial in Fort Lauderdale, Fla., on Tuesday for allegedly helping thousands of Americans avoid paying taxes by concealing up to $20 billion in secret Swiss bank accounts.

Weil, 54, was the third-highest ranked executive at the Zurich-based wealth management giant and was charged by U.S. authorities in 2008. An international arrest warrant was issued in 2009. If convicted, he faces up to five years in prison for conspiracy to commit tax fraud.

"We are preparing diligently for trial," said Weil's New York-based attorney, Aaron Marcu.

The United States in recent years has stepped up its pursuit of Swiss banks for their role in aiding tax evasion and increasingly pressured individual bankers. Since 2009, the Justice Department has charged more than 70 taxpayers and 30 bankers and advisers in a probe of offshore activities.

Authorities are also examining whether 14 Swiss banks had roles in helping potentially tens of thousands of Americans avoid paying billions of dollars in taxes.

Weil, 54, pleaded not guilty after being extradited to the U.S. from Italy last year. He was arrested while on vacation at an upscale hotel in the northern Italian city of Bologna and was held for nearly two months in an Italian jail.

He was freed on bail of $10.5 million in December, with the judge agreeing to let Weil stay with friends in New Jersey.

Weil headed the bank's worldwide private banking, and is believed to have the names of some of the world's wealthiest families who held Swiss bank accounts. Nevertheless he hasn't reached a deal with federal prosecutors as has happened in previous whistleblower cases.

"The government turned it down," said David Weinstein, a former federal prosecutor now a partner at Miami law firm Clarke Silverglate. "They still want to send a strong message to foreign banks," he added.

In May, former UBS banker Martin Lack was sentenced to five years of probation after pleading guilty to a single conspiracy count. That same month Credit Suisse became the largest bank in decades to plead guilty to a U.S. criminal charge for helping Americans evade taxes, agreeing to pay more than $2.5 billion in penalties. That dwarfs a $780 million penalty that Weil's former employer, UBS, paid to settle a U.S. tax dispute in 2009.