Ports and rail operator Asciano says a five-year extension of an agreement with privately-owned logistics company Linfox will generate revenue of up to $400 million.

Asciano's Pacific National rail business' current contract to supply rail haulage to Linfox to move containers interstate was due to expire on December 31.

That agreement had now been extended for at least five years, beginning on January 1, 2013, Asciano said today.

"The contract is expected to generate revenues of up to $400 million over the next five years," it said.