The Commerce Commission has pushed back its decision on Vodafone's purchase of TelstraClear until next week.
The regulator was scheduled to release a decision today on whether the $840 million takeover could go ahead, but its website says a ruling is now due on October 30.
The sale was announced in July and according to commentators will give Vodafone more clout to challenge Telecom.
Telecommunications Users Association of NZ chief executive Paul Brislen said at the time that competition between the two would bring better and cheaper deals for customers.
"Potentially it should be really good for the consumer. But there is always a danger that they fall back and become a duopoly ... and just not compete properly," he said in July.
"I don't think that's going to happen. I think they will get vigorous in terms of competition because suddenly Vodafone can compete right across the board with Telecom.
"Nobody's ever been in a position to do that before so having that capability, it would be foolish not to use it."