The U.S. Office of the Comptroller of the Currency issued new policy guidance that lays out how national banks can maintain crypto assets to be used for the payment of blockchain networks' "gas fees."

In what's known as "interpretive letter No. 1186," the agency said Tuesday that the banks can keep on their balance sheets digital assets they think will reasonably be required for their operations.

Blockchain networks routinely require the use of their own specific token as a fee for transactions, so banks that wish to handle such activity need to have the necessary assets on-hand. Activity "explicitly allowed under the Guiding and Establishing National Innovation for U.S. Stablecoins Act" will require banks needing to pay network fees as an agent for customers or as part of its custody operations, the letter said.

The need for banks "to pay network fees to facilitate otherwise permissible crypto-asset activities and to hold, as principal, amounts of crypto-assets on balance sheet necessary to pay network fees for which the bank anticipates a reasonably foreseeable need is permissible for the bank," the OCC concluded

U.S. banking regulators — also including the Federal Reserve, Federal Deposit Insurance Corp. and the wider Treasury Department — are already working on writing new regulations to govern stablecoin issuers and activity, based on the new GENIUS Act requirements. But those rules aren't yet in place for the law approved earlier this year.

The OCC has reversed years of hesitation about letting regulated banks engage in digital assets activity with the arrival of the pro-crypto administration of President Donald Trump. The agency is now run by Trump appointee Jonathan Gould, who was confirmed by the Senate in July.

Read More: What Are Ethereum Gas Fees?