Australia's largest iron ore ports were shut down on Monday ahead of tropical cyclone Rusty which is building off the resource-rich west coast.

The Bureau of Meteorology issued a cyclone warning stretching from Mardie, 1,200 kilometres (745 miles) north of the state capital Perth, to Cape Leveque in Western Australia's far north.

It said the cyclone, which is a category 2 on the five-level scale, was likely to intensify as it slowly approaches land.

"There is a high risk that Rusty will cross the coast as a severe tropical cyclone," it said in a statement.

"However, the slow motion of the cyclone means that the crossing time and location is uncertain."

By Monday afternoon Rusty was estimated to be about 295 kilometres (183 miles) north of Port Hedland and almost stationary.

Port Hedland, a major iron ore export hub for BHP Billiton and Fortescue Metals, closed early Monday.

"All port terminals, infrastructure and services are secure and fully prepared for the arrival of 'Rusty' in line with existing port cyclone plans," the port authority said in a statement.

"Conditions are forecast to steadily deteriorate over the next 36-48 hours with increasing winds to 70-plus knots by late Tuesday and 100 knots when the system crosses the coast on Wednesday afternoon."

Major iron ore exporter Rio Tinto said ship loading at Cape Lambert had finished late Sunday while Dampier was due to follow suit late Monday.

The weather bureau warned that Rusty, a large, slow-moving tropical cyclone, is likely to result in higher than usual rainfall in the Pilbara and western Kimberley and could trigger flooding.

"Rusty's intensity, size and slow movement is also likely to lead to a very dangerous storm tide as the cyclone centre nears the coast," it said.

"Tides are likely to rise significantly above the normal high tide mark with damaging waves and very dangerous coastal inundation."

Cyclones are a common feature of Australia's warmer months on its northeast and northwest coasts.

-- Dow Jones Newswires contributed to this report --