May 24 (Bloomberg) -- UBS AG, the Swiss bank seeking $15.6 billion from shareholders to replenish capital after subprime- related writedowns, said it may face more losses from holdings in both U.S. and global mortgage markets.

UBS had losses on non-U.S. residential and commercial real- estate securities in 2007 and the first quarter of this year which ``could increase in the future,'' the Zurich-based bank said in a prospectus for the rights offer published on its Web site late yesterday. It didn't give any more details.

The bank is also evaluating whether to limit or discontinue one or more of its so-called U.S. reference-linked note programs, which ``could result in a charge to income,'' it said.

UBS had created 10 such programs, which sold bonds referenced to a pool of asset-backed securities held by the bank, with a face value of $16.9 billion. At the end of March, the bank's net exposure to reference-linked notes was $8.9 billion.

UBS, which sold $15 billion in subprime and Alt-A bonds to a fund managed by BlackRock Inc. to reduce risk, still has more than $45 billion in U.S. mortgage-related assets, $8.6 billion in leveraged finance commitments and $10.4 billion in student loans on its books. The bank aims to replenish capital after about $38 billion in writedowns related to the U.S. subprime crisis.

UBS spokeswoman Sabine Woessner, contacted by Bloomberg News, said the bank doesn't provide information beyond its statements in the prospectus.

31 Percent Discount

The bank said May 22 that shareholders can buy seven new shares for every 20 held at 21 Swiss francs ($20.55) each, a 31 percent discount to the previous day's closing price. The company, which already got a 13 billion-franc capital injection this year, plans to sell 760.3 million new shares, which are due to start trading on June 13, for net proceeds of about 15.5 billion francs.

Chief Executive Officer Marcel Rohner told Bilanz magazine in an interview published yesterday that any further writedowns related to the U.S. mortgage market won't be as large as the $19 billion first-quarter markdown UBS announced on April 1.

The world's biggest banks have suffered about $383 billion in writedowns and credit losses since the subprime crisis began last year, and raised about $270 billion to replenish capital.

To contact the reporters on this story: Elena Logutenkova in Zurich at elogutenkova@bloomberg.net;

Last Updated: May 24, 2008 09:43 EDT