On Monday, Sprint announced it had plans to expand its LTE coverage in 100 more markets "in coming months," including major markets such as Boston, Chicago, Los Angeles, Memphis, Miami, Nashville New York, Philadelphia and Washington. The timing of the announcement was viewed by analysts as a clear attempt to woo next-generation iPhone customers, even though Sprint hasn't said when those 100 markets will have LTE service.

In July, Verizon had reached with LTE, while AT&T .

Market research firm IDC recently reported that Verizon had more than 9 million LTE subscribers in the first quarter of 2012. The next biggest markets were in South Korea and Japan, where South Korea's SK Telecom Co., ranked second with 2.75 million subscribers and Japan's NTT DoCoMo was third with 2.23 million.

While the interest in LTE by U.S. carriers is robust, IDC also noted that could delay LTE deployments there. In addition to rollouts of LTE by Verizon, AT&T and Sprint in the U.S., T-Mobile plans to roll out LTE in 2013.

"It is imperative that LTE is an available option for each operator to compete in the [U.S.] market," IDC noted in a recent report. "Consumers will continue to demand high-speed data, and operators must be well-positioned in response to this demand."