* Q4 loss/shr $3.23 vs EPS $2.24 year ago
* Shares down 2 pct in extended trade
Feb 29 (Reuters) - MBIA Inc swung to a fourth-quarter loss, as the U.S. bond insurer booked $1.7 billion in pre-tax loss on insured credit derivatives.
"The fourth quarter brought the largest quarterly reduction in risk in our structured finance portfolio since the beginning of the financial crisis," Chief Financial Officer Chuck Chaplin said in a statement.
"Including 2012 to date, we have commuted or agreed to commute almost $24 billion of potentially volatile liabilities since the end of the third quarter."
For the fourth quarter, the insurer posted a loss to common shareholders of $626 million, or $3.23 per share, compared with a net income of $451 million, or $2.24 per share, last year.
MBIA's adjusted pre-tax loss narrowed to $252 million from $311 million in the year-earlier quarter, while its adjusted book value was down 6 percent to $34.50 per share.
The company's shares, which have risen more than 40 percent in the last three months, were down 2 percent at $10.52 in extended trading. They closed at $10.78 on Wednesday on the New York Stock Exchange.