In June Rio Tinto received a letter from the secretary-general of the office of the Guinea president querying the validity of the government decree for the mining concession.

The issues seem far from clear. A Reuters report quotes Guinean Mines Minister Ahmed Kante saying on Tuesday that Rio Tinto's planned $6 billion Simandou iron ore mine was on track and would benefit both Guinea and the company, The Australian reports.

The statement appears to be an effort to allay concerns over the legal status of the project.

A letter sent to Rio by the secretary-general of Guinean President Lansana Conte's office in June queried the validity of a decree giving Rio access to the ore, but the mining company insisted its legal status was secure.

Six weeks ago it was revealed that the politically unstable West African nation was threatening to withdraw Rio Tinto's rights to mine one of the key assets in its battle against a hostile $177 billion bid by BHP Billiton.

In what seemed a divide between Guinean President Lansana Conte and the country's parliament, Rio was told in June that a document outlining its legal rights to the high-grade Simandou iron ore deposit was "stained with irregularities'' and Rio's apparent intentions were to freeze development of the asset.

In a letter dated May 22 and sent to Rio chief executive Tom Albanese, Guinean Secretary-General to the President, Sam Mamady Soumah, said Rio would be stripped of its mining concession for Simandou and only issued with a new one if it complied with Guinea's mining code.

Rio has identified Simandou, expected to start production in 2013, as a key project in the company's plan to raise annual output to 600 million tonnes.

Rio said at the weekend it had "received correspondence from the President of Guinea purporting to rescind the Simandou mining concession''.

"Rio Tinto negotiated and executed the Simandou mining concession in full transparency with the Guinea Government and is currently in discussion with relevant ministers with a view to resolving any issues,'' the company said.

Simandou has 2.25 billion tonnes of iron ore and was expected to have initial production of 70 million tonnes a year.