The next head of Verizon Communications expects U.S. regulators to approve rival AT&T Inc's proposed $39 billion purchase of T-Mobile USA due to the company's need for more wireless airwaves.

I'd say the merger will probably go through. It's a merger AT&T probably had to do, Verizon Chief Operating Officer Lowell McAdam said in a webcast of the Fortune Brainstorm Tech conference.

McAdam, who is slated to become chief executive of Verizon by year end, said the deal made sense for AT&T, which needs more wireless airwaves, and that the only surprising aspect was that it did not happen sooner.

In contrast, Sprint Nextel , the No. 3 U.S. mobile service, has been loudly urging U.S. regulators to reject the AT&T/ T-Mobile USA deal for fear of damage to competition.

The acquisition will vault No. 2 U.S. mobile service AT&T and No. 4 U.S. mobile service T-Mobile USA well ahead of current market leader Verizon Wireless.

Verizon Wireless is a venture of Verizon Communications and Vodafone Group Plc . T-Mobile USA is a unit of Deutsche Telekom .

(Reporting by Sinead Carew; editing by Matthew Lewis)