When the Federal Reserve raised benchmark interest rates lastmonth, it took North Carolina lender BB&T Corp. less than anhour to announce it was passing that cost along to borrowers.Depositors, however, have yet to see the benefit.

For many investors, such discipline means U.S. banks are aboutto feast on rising interest rates — profiting froma fatter margin between what they charge for loans and the rewardsthey offer depositors who provide the funds. Now, a small butgrowing chorus of senior executives and analysts is signaling thatresolve may fray and that shareholder optimism is too high.

Banks are under unprecedented pressure to break ranks andcompete for deposits. Compared with past cycles, more savers areweb-savvy — able to comparison shop and transfermoney online to firms offering better deals. Money-market fundsthat suffered for years with near-zero rates are eager to lure backcustomers. And new liquidity rules encourage banks to draw morefunding from consumer deposits, pushing lenders to fight for thoseclients.