Bank of New York Mellon Corp reported a third-quarter net loss after a charge to restructure its investment portfolio, but earnings excluding one-time items topped expectations and its shares climbed almost 3 percent.

The company took a $4.8 billion pretax charge to restructure its investment securities portfolio, which has seen heavy losses on complex mortgage and debt securities amid the financial crisis.

The world's largest trust bank said on Tuesday it lost a net $2.5 billion, or $2.05 per share, in the quarter, compared with earnings of $303 million, or 26 cents a share, a year earlier.

Excluding investment securities losses and other special items, the company earned 54 cents per share. On that basis, analysts had forecast 48 cents, according to Thomson Reuters I/B/E/S.

The bank's shares were at $28.00 in premarket trading, up 2.8 percent from Monday's close of $27.23 on the New York Stock Exchange.

Bank of New York Mellon, which focuses on securities services for institutional clients and asset management, said assets under custody slipped 1 percent on a year ago to $22.1 trillion, while assets under management fell 9 percent from a year ago to $966 billion, excluding securities lending assets. Securities lending assets fell 36 percent on a year ago to $299 billion.

Its investment securities unit lost $4.8 billion pretax compared with a net loss of $162 million in the third quarter a year earlier.

The company is restructuring $8.5 billion securities to reduce risk in this investment portfolio, and it has sold $3.6 billion of the lowest quality securities.

We took advantage of the recent strength in the fixed income markets by selling or recognizing losses on a significant portion of our investment securities portfolio, Chief Executive Officer Robert Kelly said.

Bank of New York Mellon in August paid $136 million to redeem U.S. Treasury Department warrants to buy its stock, and in June it bought back $3 billion of preferred shares it had issued to the government.

(Reporting by Christopher Kaufman and Elinor Comlay; editing by John Wallace and Maureen Bavdek)