Global miner Rio Tinto has obtained $226.4 million in funding for the expansion of its iron ore operations in Western Australia's Pilbara region.

The diversified, British-Australian group can now issue dredging contracts as part of early works on the development of its port at Cape Lambert.

The port expansion is in line with lifting the export capacity of Rio's Pilbara operations to 330 million tonnes a year, Rio Tinto said in a statement today.

The miner also proposes an additional 1.8km, four-berth jetty and wharf at Cape Lambert to boost its present annual limit of 80 million tonnes by a further 100 million tonnes. It intends to grow its Pilbara iron ore operations output to 330 million tonnes a year by 2016.

The dredging activities would assure subsequent decisions on the growth of operations could be executed as fast and efficiently as possible, said Sam Walsh, Rio Tinto chief executive Iron Ore and Australia.

''Rio Tinto has a proven track record of managing large-scale iron ore expansion projects, and this decision should be seen in that light.

''It is important at this stage that we advance this process in an orderly manner, and this decision does that.''

According to Mr Walsh, the dredging work counted on government and other approvals, most notably that of the Robe River joint venture partners with regard to the Cape Lambert port.

He warned that continuing uncertainties remained around the federal government's mine tax plans.

"While the Australian government's decision to abandon its resource super profits tax in favor of the proposed minerals resource rent tax was a major step forward, we remain cautious over what legislation will finally be in place," Mr Walsh said.