DES MOINES, Iowa (AP) â¿¿ Bank stocks were slipping into negative territory Tuesday, feeling the downward pressure from a potential ratings downgrade for the 15 countries that use the euro and for Europe's bailout fund. The downgrade threats came from the American rating agency Standard & Poor's. If S&P does downgrade those countries' credit ratings, that could increase the risk of them defaulting on their debt, which some analysts fear could weaken the U.S. economy further creating credit problems for U.S. banks. Shares of many regional banks fell by early afternoon. Cullen/Frost Bankers Inc. fell 22 cents to $51.03, Iberiabank Corp. was down 30 cents to $49.49, and Bank of Hawaii Corp. slid 38 cents to $42.39. First Horizon National Corp. was down 35 cents, or 4.4 percent, trading at $7.43, and Bank of the Ozarks Inc. fell 12 cents to $27.79. Some major banks hovered between positive and negative territory. Bank of America Corp. fell 3 cents to $5.77, and Bank of New York Mellon was up 18 cents, trading at $20. Wells Fargo & Co. rose 3 cents to $26.77. Citigroup Inc. fell 49 cents to $29.34, and JPMorgan Chase & Co. was down 35 cents to $33.16. Not all analysts believe banks are at such risk, especially regional banks. In a monthly review of local and regional bank stocks, Wunderlich Securities analyst Kevin Reynolds said they have outperformed the S&P 500 Index, as a group, for more than two decades. Coupled with below-average stock valuations, all indications are that the banking industry is poised to outperform the broader market over the long term as the economy recovers. He points to several indicators of bank health: â¿¿ Unemployment is improving. The national rate fell to 8.6 percent in November, its lowest point since March 2009. The nation's output measured by Gross Domestic Product increased for the ninth consecutive quarter in the third quarter.