In the coming months, some American consumers will embark on an experiment that will finally begin to answer a question with multibillion-dollar implications for the nation’s credit-card companies, mobile-phone carriers and tens of thousands of merchants doing business from coast to coast.

Will U.S. shoppers embrace the chance to make store purchases with a simple swipe of their smart phones? Such a system would eliminate the need to carry plastic credit cards and would accelerate the evolution of the mobile phone into an all-purpose device useful not only for talking, reading e-mail and listening to music, but also for handling financial transactions.

Yet, U.S. consumers have historically lagged well behind their counterparts in Asia, Scandinavia and elsewhere in adopting new uses for mobile devices. Many see the concept of one-swipe smart-phone shopping as a potential security nightmare, a bad dream littered with such goblins as lost or stolen phones, erroneous charges, and invasions of privacy, courtesy of aggressive retailers.

The issue is taking on urgency amid new reports that the nation’s two largest mobile providers — AT&T and Verizon — are on the brink of a major pilot project to test the use of smart phones as credit cards in up to four cities. As for the projected consumer buy-in, industry experts are predicting that the smart phone will gain on plastic credit cards — but at a slower pace than overseas.

“[Smart phones] have to be more convenient than credit cards, possibly cheaper and secure,” says Shawndra Hill, a professor of operations and information management at Wharton. In addition, the enthusiasm of store owners ultimately will prove as essential to the success of the experiment as that of consumers, Hill and other experts note. “Of course, merchants will have to accept the proposed type of payment,” Hill points out. “In order to get merchant buy-in, the new system will have to be easy to use and cheaper with respect to transaction fees and equipment compared to … credit cards.”