Speaking at the Television Critics Association's Press Tour in Beverly Hills today (July 24), he said that having two cycles per season of the talent show is no different to other series on rival networks.
"Almost every reality franchise does two cycles a season, and one could argue that American Idol and The X Factor are the same show.
"We're obviously cautious about expanding it. But we've also done some things to the format to ensure that it's an even better show."
NBC reality boss Paul Telegdy also dismissed concerns over Howard Stern's appointment as a judge on America's Got Talent, following the lack of a ratings boost since his arrival.
"Given the television landscape, we're thrilled with the performance of the show and would be delighted if Howard wants to come back," he said.
It has been rumoured that The Voice will introduce the spinning chairs into the Battle Rounds stage when it returns for a fall run this year.
Robert Greenblatt also spoke about the upcoming fourth season of Community.