WASHINGTON — The Justice Department’s top antitrust enforcer said on Tuesday that he supported limits on how much of the nation’s airwaves a single wireless company could hold, a condition that could keep AT&T and Verizon from bidding on certain blocks of airwaves during auctions.

William J. Baer, the assistant attorney general who oversees the antitrust division, told a Senate subcommittee that limits were needed to promote competition in the market for wireless broadband service.

The remarks echoed comments filed by the Justice Department last week in response to a Federal Communications Commission request for recommendations on how public airwaves, or spectrum, should be allocated. The F.C.C. sought the comments in preparation for the auction, in 2014, of spectrum that it is hoping to reclaim from television broadcasters.

In its filing, the antitrust division said it supported auction rules that would ensure smaller carriers could continue to compete for wireless customers, but it avoided saying that a strict limit, or screen, was the best way to go about it. Currently, the F.C.C. looks at acquisitions of new spectrum on a case-by-case basis, seeking to keep any one company from dominating a given market.