New Zealand's large ports are facing delays from a range factors, including some vessels just not arriving.

Shippers Council chairman Simon Beale says there needs to be good forecasting for shipping lines.

But he says some vessels have been delayed coming to New Zealand after port strikes in Sydney.

Beale told Mike Hosking operational changes following a recent death at Ports of Auckland, are also having an impact.

"Some vessels are going to Tauranga Port instead, which then impacts cargo movements on rail."

Beale says it could take until Christmas to clear the backlog.

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