U.S. Bank and Bank of America got together this spring on a system that lets people instantly pay money to a friend on a smartphone — with a crucial difference.

U.S. Bank charges $6.95 for the service. Bank of America offers it for free.

“There’s already a bit of a discord between us and the other bank that came out with one of the real-time payments,” Richard Davis, U.S. Bank chief executive, told analysts and investors last month. “We have to make sure that the business of banking doesn’t become a utility in the minds of the consumers where they expect everything to come without a value price to it.”

The conflict highlights an upheaval in banking around the emerging service known in tech and banking as peer-to-peer payments. Fast-acting firms like PayPal, Venmo and Square have already attracted millions of users and handled billions of dollars’ worth of transactions in which people pay someone else with a tap on a screen rather than handing over some bills and coins.

The firm that becomes dominant in peer-to-peer payments will help shape the future of transactions with merchants, who long have yearned to escape the control of card networks like Visa and MasterCard.

At the moment, PayPal has 179 million users worldwide, and its mobile subsidiary, Venmo, reported $3.2 billion in transactions in the first quarter, more than double the volume a year ago. Snapchat and Square both let people send cash to their friends quickly. On Snapchat, all users do is type the amount in a message and it shows up in the other person’s bank account. Facebook Messenger also is rolling out its own payments service.

The nation’s largest banks, which jointly own a network called clearXchange, still have major advantages.

They control most customers’ cash accounts. They alone can offer true real-time service for now. And they believe they have the potential clout with clearXchange and its 28 million registered users to attract customers from many more financial institutions and develop the critical mass to muscle out the competition.

But they have lost ground, particularly among young people, to slick apps that allow customers to move money — not instantly but quickly enough. And in September, payments through apps not controlled by banks will be able to get faster, when the Automated Clearing House adds two new windows for payments to clear during the day.

“Peer-to-peer is definitely something that the banks have taken their eye off of,” said Michael Moeser, an analyst with digital financial consulting firm Javelin. “As consumers begin to use other apps like Venmo, Square Cash, Snapchat and Facebook, there’s a degree of disintermediation — I’m not using U.S. Bank, I’m using Snapchat.”

Chase Quickpay and Wells Fargo’s SurePay both already offer peer-to-peer payments, though not in real time, and not with the elegance or simplicity of an app like Venmo, which has caught fire with college students.

U.S. Bank’s standard peer-to-peer payment service, which closes transactions in up to three business days, is free. But the bank is charging for instant payments — which it believes customers want — because offering the service required investment and the company sees the option as a premium feature.

“The principle of charging for speed and convenience is obviously not something that we invented,” said Gareth Gaston, a U.S. Bank executive vice president. “The principle of offering a base service for free, that’s completely fine, and if you have a need to speed it up, then you pay for more.”

Wells Fargo will likely be the third large bank to offer instant payments on the clearXchange network, expecting to roll out the service this summer, company officials said. They would not say whether the service will be free. Then Wells Fargo, Bank of America and U.S. Bank customers will be able to send each other money instantly. The network will be more valuable as more banks and their customers use it.

“Person to person payments can only work if you have a large network of people using that network,” Gaston said.

But it’s not clear that most consumers need most payments to be instant, and it’s a rare transaction that justifies a $6.95 charge, said Moeser, the analyst with Javelin. A last-minute bill payment, for instance, might qualify.

“It’s a great product for somebody who is late on a payment or someone who really needs to make sure that payment gets done today,” Moeser said. “At that price level, though, it’s not going to attract consumers who want to make it part of their regular payments.”

U.S. Bank and Bank of America are still in the early stages with their instant payment service, and won’t say how many people are using it. Gaston at U.S. Bank said he believes most people will be moving money to other people with their phones within five years, and added he’s confident that banks will be at an ­advantage.

“For sure, customers trust banks more than they trust start-ups,” Gaston said.