T-Mobile USA has proposed a one-third limit on the amount of below-1 GHz spectrum carriers can acquire in an individual market in the FCC’s upcoming auctions.

T-Mobile outlined the proposal Friday in an FCC filing that insists the suggested spectrum aggregation limits will promote competition while still allowing AT&T and Verizon to “participate extensively in the auction.”

Verizon in July argued that a one-third limit, if applied upfront, would bar it from acquiring spectrum in 9 of the top 10 markets while one-third limits including either 50 or 70 MHz available at auction would bar 7 of the top ten for the carrier.

T-Mobile argued that if 70 MHz were available at auction, Verizon could acquire a 5×5 MHz license in markets covering approximately 90 percent of the population and a 10×10 MHz license in markets covering more than half of the population. Under those same circumstances, AT&T could acquire a 5×5 MHz license covering about 90 percent of the population and a 10×10 MHz license covering about one-third.

The FCC is still in the rule-making process for its upcoming 600 MHz incentive auction.

T-Mobile’s new proposal joins the Dynamic Market Rule, aimed at preventing resource concentration, already filed with the FCC. AT&T came out against the Dynamic Market Rule proposal, stating in a blog post it would “almost certainly doom the auction.”

T-Mobile Vice President of Federal Regulatory Affairs Kathleen Ham responded that “Without adequate competitive safeguards, there is nothing to stop the largest two carriers from walking away with all the 600 MHz low-band spectrum.”