U.S. banks, after spending much of the last year bracing themselves for higher bond yields, are now resigning themselves to at least another few quarters of low rates, executives and analysts said.

Banks including Wells Fargo & Co and PNC Financial Services Group are contemplating steps like investing their extra cash at current low yields or using derivatives that pay off if rates stay low.

"We are seeing more management teams acknowledging the prospect and reality that we remain in a lower for longer [interest-rate] environment," said Christopher Lee, a portfolio manager who specializes in financial companies at Fidelity Investments, which has $1.15 trillion invested in stocks across the world, in an e-mail.

Lee added in a telephone interview that "over time, you've got to throw the towel in" if the benefits of rising rates keep failing to materialize.

Positioning for higher rates has cost the 20 largest U.S. banks somewhere between $2.5 billion and $3 billion of income each quarter, roughly 6 percent of their collective profits before taxes, said Marty Mosby, a bank analyst at Vining Sparks. 

Those estimated costs come from banks refraining from investing customer deposits in longer-term bonds, and holding the funds instead in cash or short-term investments, which offer much lower returns.

In addition to foregone revenue, the strategy is also having more tangible costs.

In the fourth quarter, Bank of America Corp marked down a bond portfolio that it uses to hedge interest rate risk by around $600 million, leading it to miss analysts expectations. 

Regions Financial Corp said on Tuesday that its net interest margin, a measure of how profitably it loans out its deposits, would decline even more in 2015 than it did in 2014 if rates stay low this year. Some loans that banks make, including mortgages, carry fixed rates, which in the current environment will generate lower returns for their whole lives for lenders.

STUCK

Almost all major U.S. banks have received far more money from depositors than they can actually lend out, and instead of putting all of that extra cash to work by investing in bonds, many decided to hold off at least some of their investments until yields rose, so they could earn more. For much of last year, investors expected the Fed to start raising rates in 2015. If driven by heightened inflation expectations, those rate hikes could lift longer-term bond yields.

But as bond prices have risen and yields have fallen in recent weeks, banks' potential returns have slipped as well.

"They're stuck waiting for an event that may or may not happen any time soon," said Nancy Bush, a bank analyst at NAB Research LLC.

Bond yields in the United States have fallen in recent months for a series of reasons, including investors' increasing pessimism about the pace of economic growth in Europe andChina, lowering yields around the world and making the United States look relatively attractive. Concerns about worldwide growth have also increased the appeal of U.S. bonds as a safe-haven.

The 10-year U.S. Treasury yield was 1.87 percent on Thursday, a steep drop from September, when it stood at 2.6 percent. 

Shifting rates and bond yields can affect banks in multiple ways. For a big chunk of banks' investment portfolios, falling yields will boost banks' capital levels, which is a positive. And if the Federal Reserve lifts short-term rates, banks' floating-rate loans will generate more income.

But recent drops in yields are clearly cutting into earnings, hurting returns on both bond investments and fixed-rate loans. Banks will not usually compensate for lower bond yields by buying riskier securities such as junk bonds, because they prefer to take credit risk in their loan books.

The earnings pressure from low interest rates is weighing on bank shares, according to Fidelity's Lee. The KBW index of bank stocks was down 9.99 percent since the beginning of 2015, over five times the 1.77 percent decline in the S&P 500.

Some executives are planning to act sooner rather than later. A scenario where bond yields stay lower-for-longer "probably emboldens us a little bit additionally to convert what's cash today into [securities] over the course of the year," Wells Fargo finance chief John Shrewsberry told analysts last week.

In a shift for how it views its interest-rate exposure, PNC, which had previously said it was giving up $200 million each year by not investing its extra cash, has begun to use derivatives to increase its revenues until it a rate hike finally comes, said Kevin Barker, a bank analyst at Compass Point Research & Trading, LLC.

There is another option for other banks for boosting profits that does not rely on market conditions: trimming costs. Senior executives at JPMorgan Chase & Co are pressing their underlings to look at ways to cut expenses more aggressively, a person familiar with the matter told Reuters on Jan 14.

But some bank executives said, even if rates stay lower for longer than anticipated, that making their balance sheets ready today for higher rates is a form of cheap insurance against a scarier scenario.

"We're going to be very patient," JPMorgan Chief Executive Jamie Dimon told reporters last week. "There's far more downside with rapid rates rising and rising too much than anything else for us."