Aug. 13 (Bloomberg) -- Senior executives at UBS AG were aware that some of their bankers had risked breaching U.S. securities laws at least 12 months before American authorities started an investigation into the bank, the Financial Times reported, citing an internal letter.

The letter, written in response to a whistleblower in May 2006 by Peter Kurer, then the bank's general counsel, to former UBS banker Bradley Birkenfeld, shows that senior individuals at the bank knew at that time that UBS may face problems because of inadequate securities registration, according to the newspaper.

Both Marcel Rohner, now group chief executive officer and then head of private banking, and Lawrence Weinbach, a bank director who sits on the board's audit committee, were copied on the letter, the FT said.

The whistleblower referred only to potential breaches of securities law and not to tax evasion issues being investigated by the U.S., the FT cited unidentified UBS officials as stressing. Kurer, who is now chairman of UBS, acted quickly to tighten procedures after investigating the whistleblower's allegations, the officials told the FT.

There was no immediate response to messages requesting comment left by Bloomberg News outside of office hours with Mark Arena, Americas head of corporate communications for UBS, or Rohini Pragasam, head of media relations.

To contact the reporter on this story: Andrew Shepherd in London ashepherd5@bloomberg.net

Last Updated: August 12, 2008 20:55 EDT