Wells Fargo & Co. expects low interest rates to drive down its net interest income year over year by more than 11% in 2020. In its first-quarter earnings report in April, the bank withdrew its previous forecast for a percentage drop in the mid-single digits, citing market volatility and uncertainty about the economic outlook.

In addition to the low overall level of rates, CFO John Shrewsberry said, the new forecast reflects a drop in the London interbank offered rate to nearly zero after central bank interventions helped ease liquidity conditions behind a spike in late March and early April. Many loan prices are tied to Libor.

Shrewsberry also said deposit rates are taking longer to decline than expected.

"We do expect, however, by the end of the year, that our all-in deposit costs look something like it did at its lowest levels in the early to [middle] part of the last decade," he added, speaking at the Morgan Stanley Virtual U.S. Financials Conference. "Deposit costs have crashed as rates have come down to zero. So that will be a benefit later in the year."

Another factor behind the forecast is the asset cap that the Federal Reserve imposed on Wells Fargo over a variety of consumer abuses and control issues. Despite relatively weak loan demand, Shrewsberry said, the bank may have otherwise offset some of the net interest income pressure by adding securities.

In line with previous statements by executives, Shrewsberry declined to give a time frame for when the cap might be lifted. He said the bank is "positioning ourselves and preparing ourselves to live under $1.952 trillion of assets for the foreseeable future."

He said the main lever for doing so is keeping clients' "nonoperational" deposits that could be placed with other banks or money market funds off Wells Fargo's balance sheet.