Rio Tinto has committed an additional $1.3bn to the development of the Simandou iron ore field project in Guinea.
"Rio Tinto is accelerating the development of the Simandou iron ore project in Guinea with the approval of a further $211M for continued studies and $1.117bn of funding for commitments for early works and procurement," the mining group said.
"This funding will allow the project to move forward towards first shipment of ore by mid-2015."
The announcement brings the total amount spent or committed to the project to $3bn, including $700M paid to the Guinean government to secure the right to mine in two sections of the huge deposit.
Work has already begun on the marine off-load facility near the preferred port site of Ile Kabak, 50km south east of Conakry, enabling the introduction of heavy equipment for construction.
In-country support services such as air-charter, extensive camp works and associated infrastructure are also in progress, as is the commencement of earthworks for the 650km rail line.
Rio Tinto added it was working towards securing regulatory approvals to allow it to enter into a $1.35bn deal to sell a 44.65% stake in Simandou to Chalco.