Commerce through the use of mobile devices will grow by leaps and bounds, says American Express CEO Ken Chenault.

Indeed, it represents a "gigantic opportunity," he tells Fortune. "Mobile will redefine how commerce is done."

And who's going to dominate the space?

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"Clearly there are five platforms that will play an important role and be very powerful: Amazon, Apple, Google, Facebook, and Alibaba," Chenault proclaims.

But startups will play a role too, he maintains. "More and more, startups will be able to connect to these services to scale quickly," he notes.

"The opportunity for startups to redefine the power of mobile is incredible."

While the payment system is going through some major changes, "plastic is not going to go away," at least for the short term, Chenault states.

"You are going to see a demarcation between payment companies. There are going to be those that stay in the status quo, and they're going to focus on facilitating payments. That is a mistake. They will be reduced to a commodity," he said.

Then, "there will be those companies who will focus on the entire commerce journey, and that's us."

Meanwhile, Matt Egan of CNNMoney cites three of the companies Chenault mentioned as possible stock investments: Facebook, Google and Amazon.

"Despite the pullback in valuations, the fundamentals of large-cap Internet companies haven't changed," Citigroup analyst Mark May writes in a commentary obtained by CNNMoney.

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