July 10 (Reuters) - UBS cannot comply with a U.S. request to disclose the identity of 52,000 U.S. secret account holders, the bank's chief executive Oswald Gruebel said in an internal memorandum, according to a source familiar with the situation.
Following is a timeline of recent major events at UBS:
April 1, 2008 -- Doubles its writedowns, dumps its chairman, Marcel Ospel, and seeks more emergency capital. It proposes its lawyer, Peter Kurer, as Ospel's successor.
May 6 -- Says it will axe 5,500 jobs and sell billions of dollars of ailing assets to weather the subprime crisis.
June 19 -- A former UBS banker who once smuggled a client's diamonds into the U.S. in a toothpaste tube pleads guilty to helping a billionaire hide $200 million in assets from U.S. tax authorities, part of a broader tax evasion probe of UBS.
Oct. 16 -- Announces it is to get 6 billion francs from the Swiss government for a 9.3 percent stake and is to unload $60 billion of toxic assets into a new central bank fund.
Nov. 12 -- Raoul Weil, head of UBS AG's wealth management business, is charged with conspiring to help thousands of wealthy Americans hide $20 billion of assets from U.S. tax authorities in Swiss bank accounts.
Feb. 10, 2009 - Posts a 2008 loss of 19.7 billion francs, the biggest ever loss for a Swiss company. Cuts 2,000 more jobs.
Feb. 18 - Agrees to pay $780 million and identify certain U.S. clients to settle criminal fraud charges that it assisted rich Americans to evade taxes.
Feb. 19 - U.S. tax authorities say they are still pursuing a civil lawsuit seeking to access details on 52,000 UBS clients.
Feb. 26 - Appoints Oswald Gruebel, former head of rival Credit Suisse, as chief executive, replacing Michael Rohner.
March 4 - Chairman Peter Kurer steps down. Kaspar Villiger, a former Swiss finance minister, is nominated as a replacement.
March 13 - Switzerland agrees to make concessions on bank secrecy amid global crackdown on tax evasion.
April 5 - Announces worldwide travel ban for wealth management client advisers after coming under scrutiny in the U.S. tax fraud investigation.
April 20 - Agrees to sell Brazilian business Banco Pactual for about $2.5 billion.
May 5 - Confirms a first-quarter net loss of 2 billion francs on yet more writedowns and client withdrawals. It also announces staff cuts of 10,000.
June 9 - Lock-up period ends allowing the Swiss government to covert its debt into shares. The government says it is in talks over its investment with various parties but has not yet decided to convert its notes or sell them.
June 25 - UBS says it is offering 293.3 million new shares at a price of 13.00 francs per share, a 6.9 percent discount to the day's closing price of 13.97.
-- It also says it will post a second-quarter net loss.
July 9 - A judge orders the U.S. government to say whether it was prepared to shut Swiss bank UBS AG in the United States.
July 10 - Gruebel sends a memorandum to the bank's top executives saying the bank could not comply with the U.S. request to disclose the identity of the 52,000 account holders. (Reporting by Sam Cage and Lisa Jucca; Additional writing by David Cutler, Jijo Jacob and Carl Bagh; Editing by Jon Loades-Carter)