TTR said it would agree provided the extension was only for Ngāti Ruanui and that the iwi would talk to it during the time.
It said Ngāti Rangi had indicated it would provide a cultural impact assessment on the proposal, but then declined to do so.
But Ngāti Ruanui kaiarataki Debbie Ngarewa-Packer said the tribe never made a firm commitment to do so. She strongly objected to TTR saying a commitment had been broken.
Ngāti Ruanui will provide a cultural impact assessment if TTR will make its complete application available, she said. At present parts dealing with a possible sediment plume created by the mining are redacted (blacked out) and only accessible to people who have signed a confidentiality agreement.
Having access to a full application is standard practice in resource management matters, she said.
"Our door remains open, but we will continue to insist on full disclosure and being treated with respect and in good faith."
The committee received five other comments on the request for an extension. All said more time would be useful, and several noted that Kiwis Against Seabed Mining (KASM) has asked the Environment Court to rule on whether TTR can black out portions of the application.
The court is to hear the matter in early November, and an early decision could give people time to add to their submissions.
KASM chairman Phil McCabe supported Ngāti Ruanui's request, and appreciated the EPA's response.
"The application is also horrendously complicated, and only one month for public submissions simply isn't enough time."
He said nearly 10,000 people had already made submissions - more than double those who submitted on TTR's last application - and now there was time for even more.