Transport Minister Gerry Brownlee has left open a prospect of trains, trams or buses running under Auckland's Waitemata Harbour - not just motorway traffic.
He told a public meeting in Auckland that although no decisions had been made, be believed the next harbour crossing would be "three tubes for multimodes of transport, whatever they might be".
That is despite a claim by Labour last month that the Government was poised to announce an accelerated timetable for a roads-only crossing of the harbour.
Mr Brownlee told the pre-election meeting on Wednesday night, hosted by the Campaign for Better Transport, that the Government believed 2025 remained the "right time" to start construction of a third harbour crossing.
A spokesman for Mr Brownlee said the minister was simply indicating a personal view in saying the next tunnel was likely to be multimodal.
Auckland Mayor Len Brown, who has proposed twin tunnels carrying three lanes of motorway traffic through their top halves with provision for rail below, welcomed Mr Brownlee's comment.
"There's no doubt that rail to the Shore will be needed so it's essential any additional crossing is future-proofed," he said.
A North Shore member of the Auckland Council, Chris Darby, suggested that in view of the success of the Northern Busway in easing traffic pressure on the existing bridge, the Transport Agency could consider building one tunnel for heavy or light rail (trams) to start with.