Wellington, Feb 2 NZPA - The first train from Auckland's harbour port to the Wiri inland port in south Auckland will roll across the newly completed $9 million rail link tomorrow.

Ports of Auckland and KiwiRail say the new 25km link will allow exporters to drop their goods off in south Auckland, rather than drive to the port through the city, saving 2.5 million truck kilometres a year -- the equivalent of 100,000 central city truck trips.

The Wiri inland port is close to Auckland International Airport and State Highways 1 and 20.

Ports of Auckland managing director Jens Madsen said completion of the rail exchange was a major step forward for the port company and for the Auckland region.

"New Zealand needs top quality infrastructure and a flexible mix of sea, road and rail transport options, if our economy is to grow," said Mr Madsen.

There were also big potential savings for businesses close to the Wiri inland port, he said.

"A lot of our current customers are based within 8km of the inland port. By using the rail link to the seaport, this group will be able to reduce the carbon emissions of transporting their containers by up to 25 percent," he said.

KiwiRail chief executive Jim Quinn said the rail link was a natural addition to the rail network, given its proximity to the North Island main trunk line.

"It's all part of the development of a leaner and more efficient national supply chain which benefits the whole New Zealand economy."

Ports of Auckland has been operating the 10ha Wiri site as an inland port for six years, and up until now, been using a truck-based shuttle service to link it with the city port.

Initially KiwiRail will run four services of 23 wagons a week in each direction between Wiri and the Auckland seaport.

Construction of the rail exchange began in June last year. The job included three rail sidings, 2000m of rail track and a hardstand about the size of the Britomart station. The Government provided KiwiRail's $6m contribution to the $9m link and Ports of Auckland $3m.

The rail exchange will be formally opened at a ceremony in March.