Sprint, whose CEO is the chairman of CTIA, has joined the Rural Cellular Association (RCA), the group announced yesterday at its annual convention in Las Vegas.

Sprint is now a member of both CTIA and the RCA.

Sprint’s decision to join the RCA comes one month after AT&T announced its acquisition of T-Mobile USA, a deal Sprint opposes. The merger would put nearly 80 percent of the U.S. wireless market in the hands of AT&T and Verizon Wireless, leaving Sprint in a distant third place.

The RCA has said the merger will be detrimental to the competitiveness of the U.S. wireless industry; CTIA has made no public comments about the deal.

“At Sprint, we have many issues of mutual concern with RCA members and we look forward to advocating for policies that promote competition and a level playing field across the wireless industry,” Sprint government affairs executive Vonya McCann said in a statement.

CTIA is neutral on some issues important to carriers competing with AT&T and Verizon, such as the FCC’s data roaming mandate, which the RCA supported.

CTIA’s members include AT&T, Verizon, Sprint and T-Mobile, as well as Tier 2 operators including Leap Wireless and SouthernLINC Wireless. Neither AT&T nor Verizon are members of the RCA.

“RCA is not just a rural carrier association, we’re the competitive carrier association,” says RCA President and CEO Steve Berry. “Sprint knows the issues we’re fighting for are the issues that allow them to survive.”

Berry says AT&T’s merger with T-Mobile solidified Sprint’s need for additional advocacy.

CTIA public affairs chief John Walls concedes that there is disagreement between its carrier members on some issues, but says it’s not unusual for operators to have memberships with both CTIA and the RCA. Both U.S. Cellular and Sprint now have dual membership.

“Nobody, certainly in the association world, has unanimity among its members,” Walls says. “We represent an ultra-competitive industry that sometimes has diverging interests among its members.”

CTIA’s board of directors is chaired by Sprint CEO Dan Hesse, with AT&T mobility chief Ralph de la Vega serving as chairman emeritus and U.S. Cellular CEO Mary Dillon as treasurer.

Walls says the board has recommended CTIA stay out of certain issues where there is disagreement among its members. “We do follow the direction of our board and there are some issues where we’ve decided to let the individual companies advocate as they see fit,” he says.