AT&T's rivals have asked U.S. regulators to combine a review of AT&T's proposed purchase of T-Mobile USA with their examination of its plan to buy wireless airwaves from Qualcomm Inc .

The request is the latest move in efforts by companies such as No. 3 U.S. mobile operator Sprint Nextel to derail AT&T's plan to buy the U.S. business of Deutsche Telekom AG for $39 billion.

AT&T also agreed in December to pay Qualcomm $1.93 billion for airwaves. AT&T filed last week for approval of the T-Mobile USA deal with the Federal Communications Commission.

Rivals including Sprint, Cincinnati Bell , MetroPCS Communications

and Ntelos Holdings say the FCC should look at the cumulative impact of both deals to U.S. mobile competition, rather than running separate reviews.

AT&T rejected the notion that the reviews should be combined, noting that its FCC application for the Qualcomm purchase was already 77 days into a 180-day review.

These are two completely separate proceedings and should remain so, an AT&T spokesperson said in an email.

(Reporting by Sinead Carew; Editing by Tim Dobbyn and Gerald E. McCormick)