By Dan Levine

Feb 10 (Reuters) - A former senior UBS private banker has agreed to plead guilty in connection with a criminal indictment for selling offshore tax-evasion services to wealthy Americans, according to court documents.

The former banker, Martin Lack, is a Swiss national who was indicted in 2011 in Florida on a charge of conspiracy to defraud the United States.

In a court filing last week, Lack's attorney and the U.S. Department of Justice asked a federal judge in Fort Lauderdale, Florida to set a date for Lack to plead guilty. The next day, U.S. District Judge William Dimitrouleas scheduled a hearing for Feb. 26.

Lack's attorney Peter Raben could not immediately be reached for comment on Monday, and a Justice Department representative declined to comment. The court documents do not state the charge to which Lack has agreed plead guilty.

U.S. authorities, who suspect tens of thousands of Americans are using Swiss banks to avoid paying billions of dollars in taxes, have been conducting a wide criminal investigation into scores of Swiss banks and international banks with Swiss operations.

UBS paid a $780 million fine in a 2009 settlement and agreed to hand over the names of U.S. clients with secret accounts, breaking Switzerland's tradition of banking secrecy, to avoid feared criminal charges against the bank or other executives.

Raoul Weil, the ex-head of wealth management at UBS, was arrested in last year while on vacation with his wife at an upscale hotel in the northern Italian city of Bologna. He was extradited to the United States in December and if found guilty faces up to five years in prison for conspiracy to commit tax fraud.

Weil had been scheduled for trial in Florida on Feb. 18. However, the trial was recently postponed for eight months to allow the defense more time to prepare.

In Lack's case, the indictment cited work with nine wealthy American clients, including one who traveled to a hotel in New Orleans and handed Lack $200,000 in cash to take back to Switzerland. Lack also encouraged American clients not to come forward to the IRS under a "voluntary disclosure" program that reduced fines and penalties, court papers said.

The case in U.S. District Court, Southern District of Florida is United States of America vs. Martin Lack, 11-cr-60184.