Prime Minister John Key says he's not worried by calls for a referendum on asset sales.
The Greens and their allies in the Keep Our Assets coalition are aiming to gather enough signatures for a citizens-initiated referendum by the end of next month.
Co-leader Russel Norman, speaking at a rally in Auckland on Friday, says there's "a real possibility" the Mighty River Power share float will be pushed back to March next year.
"A referendum on asset sales could be held early next year, before any of the power companies are sold," he said.
"It's only fair a referendum is held as soon as possible to give the overwhelming majority of New Zealanders who oppose asset sales the chance to cast a vote against them."
The Greens and their partners have gathered 240,000 of the 310,000 signatures they need for a referendum.
They want to deliver 380,000 because they're anticipating thousands will be struck off as invalid when the signatures are checked, as has happened in the past.
However, Mr Key says that once the authenticity of the names has been checked, which is a long process, the government has 12 months to determine the date that the referendum can be held.
"When we are satisfied that they genuinely have the required number of signatures and they are legitimate, then we'll give some consideration to when the referendum might be held," he said.
When asked by media if he was worried about a potential referendum, Mr Key said "not in the slightest".
The government wants to sell the Mighty River Power shares in November, but it has run into trouble with the Waitangi Tribunal which says the float should be put on hold until Maori water rights have been settled.
The cabinet will decide on Monday whether to go ahead or wait until March next year.