American Express' financial performance is already suffering from the pending loss of its Costco card business in U.S., pressuring the company's focus on emerging payments technology to provide a financial lift to calm nervous investors.

"We have started to see some slowing of new Costco co-brand card acquisitions which, along with any future customer behavior changes that we may experience, will likely begin to impact our performance somewhat later this year," said Jeff Campbell, Amex's executive vice president and CFO, during April 16's earnings conference call, adding the company's results are a "bit more complex" than usual.

Investors grilled Campbell about the pending Costco loss during the call. While Amex has made attempts to retain Costco cardholders, Campbell also said the company was not cutting back on its other investments. Amex is also reeling from losing an anti-trust case in court and the end of its co-branding relationship with JetBlue.

Much of Amex's investment will come in marketing, but also in technology. The renewals of other relationships with Delta, Starwood and Café Pacific will bolster performance in its co-branded merchant card segment, Campbell said.

American Express has invested in technology development centers and supports Apple Pay. This week the company also unveiled a new opportunity in Jawbone's latest fitness band, which includes Near Field Communication technology for contactless payments.

"New tech is absolutely an opportunity for Amex," said Jim Van Dyke, founder and president of Javelin Strategy & Research. "Today's newly affluent consumer values control and American Express can uniquely provide it because it controls everything on the platform."

American Express reported net income of $1.5 billion for the quarter ending March 31, up 6% from $1.4 billion last year. Diluted earnings per share rose 11% to $1.48, up from $1.33 a year earlier. In addition, the company faces some headwinds in international markets due to the strong U.S. dollar, Amex said.

Costco accounts for about 8% of Amex customer spending and about 20% of its worldwide loans. Amex may not lose all of that since it can retain the cardholders, and Campbell said about 70% of the Costco card spending occurs outside Costco. During the earnings conference call, Campbell was asked about selling the portfolio, and he declined to discuss that possibility.

In an earlier interview, Ken Patterson, the vice president of research operations and director of the credit advisory service at Mercator Advisory Group, said the finite number of retailers makes the co-branded card market a "zero sum game."

But there are still opportunities, said Phil Philliou, president and CEO of TruBeacon, adding the co-branded card space also requires innovation.

"The evolution of cobranded credit cards is that they include a mobile component, such as a mobile app with the ability to pay using the cobranded card," Philliou said.