Mining giant Rio Tinto Plc and China's Sinosteel Corp have extended their Australian joint venture to supply another 70 million metric tons of iron ore over the next five years, expanding one of the longest-running partnerships in the two countries' trade relationship.

The extension, the second in the 29 years of the Channar joint venture that has provided for the production of 250 million tons of iron ore, will add a further 30 million tons. The remaining 40 million tons will come from a separate sales agreement in force until 2021.

The venture has been heralded as the cornerstone of the China-Australia economic relationship.

"In the 50 years that we have been exporting iron ore from the Pilbara, the Channar joint venture stands out as one of the most important deals not only for our business, but for Australia's economic ties with China," Rio Tinto's iron ore chief Andrew Harding said in a statement on Friday.

Sinosteel will pay a one-off $45 million fee as well as additional production royalties linked to the iron ore price, capped at $500 million to comply with the United Kingdom listing regulations.

Under UK Listing Authority rules, Sinosteel is considered a related party of Rio Tinto's UK listed shares.