Ofcom said to provide certainty and stability it would not be appropriate for BT to launch Equinox 2, planned on April 1, until it issued its final decision.
BT wants to offer internet service providers, such as Sky, Vodafone and TalkTalk, discounts in return for moving customers to the national fibre network it is building.
Rivals such as Virgin Media O2 and hundreds of alternative fibre providers, called altnets, are investing billions of pounds to build competing networks.
Ofcom said it was not minded to stop the former monopoly provider introducing the scheme, saying it did not consider the offer to be anti-competitive.
But comments made by BT's Chief Executive Philip Jansen to the Financial Times in February, headlined "BT chief warns Openreach fibre push will 'end in tears' for rivals", caused "significant concern" at the regulator.
Ofcom Chief Executive Melanie Dawes said in a letter to Jansen, published on Friday, that the regulator was committed to network competition.
"Were it to become apparent that BT is able nonetheless to distort competition in the market, we would not hesitate to regulatory action to address this," she said.
Jansen's response, also published by Ofcom, said his comments had been taken out of context in the article and particularly in the headline.
Ofcom said respondents to its consultation had referred to Jansen's comments.
BT's earlier wholesale pricing offer, Equinox, was challenged by alternative fibre network provider CityFibre, but Ofcom decided not to intervene.
Virgin Media O2, BT's biggest network rival, has said Equinox 2 needed to be thoroughly scrutinised to ensure Openreach was not using its market power to stop providers switching to other networks.
BT shares were down 1.3% in early trade.
(Reporting by Paul Sandle; editing by Sarah Young and Jason Neely)
By Paul Sandle
