Rio Tinto says a presidential legal advisory team in Guinea is conducting a review of the mining concession for its $US6 billion ($6.35 billion) Simandou iron ore project.
The world's second largest producer of iron ore said today that it had received a letter from the secretary general of the president's office querying the validity of the decree that issued the mining concession for the project.
Rio Tinto, however, said the letter did not query the validity of the Simandou 2002 mining convention that has been approved by law and under which the concession is held.
The company last month unveiled a 2.25 billion tonne resource for Simandou, which has been touted by Rio Tinto as one of its key growth projects.
An investment decision is expected for Simandou in 2009, with first ore being mined 2013 at an initial rate of 70 million tonnes per year.
Rio Tinto said that it was in discussions with senior government representatives to "resolve what it considers to be issues based on the misinterpretation of the Simandou mining convention''.
The company has spent $US300 million on the project to date and has 1000 people on the ground conducting resource and infrastructure studies.
Rio Tinto shares lost $1.45, or 1.1%, to close at $132.10.
AAP