He said route protection work would be progressed "with urgency" in order to future-proof bus and light rail options. The proposed route will be along Dominion Road.
It was not known whether the Government would fully fund the rail project. Its estimated cost is around $1 billion. The NZTA ruled out heavy rail last year because of the cost - around $2.2 billion.
There were renewed calls for better transport links to the airport after dire congestion problems over the summer holidays.
Passengers and airline crew were caught in gridlock, some missing flights and causing delays of up to an hour for some services.
Growing numbers of passengers through the airport, aviation sector staff and workers at associated businesses and cross-town commuters have clogged roads in the area.
Green Party transport spokeswoman Julie Anne Genter said it was positive that the Government and transport officials had conceded light rail was needed, but it was "absurd" not to introduce it sooner.
It would take 10 years just to get the busway up and running, she said. The Greens wanted light rail in place by 2025.
"We have record numbers of people arriving into Auckland Airport. Traffic is a nightmare. So there needs to be an urgent solution.
"Everywhere we've invested in the rail network it's been hugely successful. We know it's proven. If we know we are going to build it, the sooner we build it, the sooner we get the benefit."
Genter said it was embarrassing that large numbers of tourists were arriving in the country to overcrowded buses and gridlock.
Labour's Auckland spokesman Phil Twyford also said light rail needed to be built as soon as possible.
"The agreement between Auckland Transport and NZTA to build light rail from the CBD down Dominion Rd to Mt Roskill and on to the airport is welcome news. The 30 year wait isn't."
Auckland Transport chief executive David Warburton said all parties now agreed that urgent action was needed on upgrading transport links to the airport.
"The agencies have agreed and confirmed through various studies that Dominion Rd is the preferred route and we all acknowledge not only the importance of the Airport Precinct and the city centre, but the public transport access and connectivity that is needed along the route."