OLUMBUS, Ga. (AP) -- Standards & Poor's Ratings Service on Friday lowered the financial strength rating for insurer Aflac Inc., a move met with surprise and disappointment by Aflac's chief executive.

The rating agency lowered Aflac's financial strength rating from "AA" to "AA-" and the company's debt rating from "A" to "A-." Concerns about the continued deterioration in global financial markets and Aflac's investment exposure to global financial institutions were cited as reasons.

S&P also placed Aflac on credit watch with negative implications.

Aflac CEO Daniel P. Amos said in a statement he's confident in the company's business model and operations.

"We are equally confident with the quality of our balance sheet and our capital position, and we believe that there is a strong need for the products we sell," he said.

Aflac is scheduled to release fourth-quarter results on Feb 2.

Shares rose 6.9 percent, or $1.59, to close at $24.49. They've traded between $22.08 and $68.81 in the past 52 weeks.

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