The year-long retreat in the price of iron ore refuses to let-up, with the commodity again sinking to a new five-year low overnight.

At the end of the offshore Monday session, benchmark iron ore for immediate delivery to the port of Tianjin in China was trading at $US75.10 a tonne, down 0.6 per cent from its previous close of $US75.50 and its lowest mark since September 2009.

The commodity has scarcely seen a positive session in the past two-and-a-half weeks after an October rally brought its price back above $US81 a tonne.

Iron ore has so far lost 45 per cent on the year after three straight quarterly declines in double-digits.

The falls have put pressure on mid-tier miners like Atlas Iron and BC Iron, while Fortescue Metals Group is quickly seeing its break-even buffer zone erode. Market heavyweights Rio Tinto and BHP Billiton -- which have been partly responsible for the commodity's price fall due to production expansion -- have greater comfort given market-leading cost positions that will see them turning a profit until the price sinks below $US50 a tonne.

The latest decline comes after ANZ Bank analysts tipped a price floor for the commodity of about $US70 a tonne.

“Substantial domestic iron ore mine closures would occur between $US70 to $US75 a tonne, creating a floor,” the bank said in a report last week.