* Signature set for next week, ends lengthy legal battle
* Details set to be disclosed shortly after signature
* Specific category of UBS client names to be disclosed
* IRS to get names of biggest account holders
* IRS seen prosecuting 150 wealthy U.S. clients of UBS
(Recasts with details from source, background)
ZURICH, Aug 14 (Reuters) - A landmark settlement that will spare UBS a lengthy and damaging U.S. tax trial is set to be signed next week and will involve the disclosure of the biggest holders of secret Swiss accounts.
"The signing will most likely take place next week," a source familiar with the situation told Reuters on Friday.
The source did not want to disclose any details from the settlement, but the New York Times said on Friday Swiss accounts in the name of U.S. residents over a certain dollar amount would be disclosed to U.S. tax authorities.
Earlier this week, the U.S. and Swiss government initialled an out-of-court settlement to end a dispute over whether the Swiss bank should be forced to disclose the names of 52,000 rich U.S. clients suspected of tax evasion.
However, the parties did not disclose details of the deal, which ends a protracted tax dispute that has damaged UBS's image abroad and threatened Switzerland's prized bank secrecy.
The details of the settlement will also be made public next week, the source added.
The New York Times said the settlement would involve UBS disclosing the names of U.S. clients who had set up offshore entities to evade taxes and those who had contact with Swiss-based UBS bankers in person, by telephone or e-mail.
Shares in UBS were up 1.28 percent at 17.44 Swiss francs, outperforming a flat DJ Stoxx European Banking Index.
The New York Times also reported that 150 American clients of UBS would likely face criminal charges related to tax evasion in the United States, citing a person briefed on the matter.
The person told the paper that several inquiries across the country were being handled by dozens of prosecutors and will result in criminal complaints.
The paper said it was unclear where the U.S. government got the client names from.
In February, UBS agreed to pay $780 million and to hand over data related to about 250 U.S. clients to settle criminal charges it was facing under a tax dispute with the U.S. government.
UBS and the Swiss department of justice declined to comment. (Reporting by Ajay Kamalakaran and Lisa Jucca in Zurich, editing by Will Waterman)