The project, which U.S.-Canadian investor Robert Friedland's High Power Exploration Inc (HPX) acquired in 2019, said in a statement it expects eventual production of up to 30 million tonnes a year. Construction is forecast to begin in 2023.
The pre-feasibility study estimated total project development costs at $2.77 billion and direct capital costs for rail and port development in Liberia at more than $600 million, it said.
The project is located deep in Guinea's mountainous interior and depends on access to neighbouring Liberia's Buchanan Port to export. HPX said it received authorisations from the Liberian government in August to move its ore through the country.
But Guy de Selliers, the chairman of HPX's subsidiary in Guinea, said he was concerned by Liberian media reports that an agreement struck in September between Liberia and ArcelorMittal could grant exclusive access to the existing railway to that company.
ArcelorMittal owns an iron ore project on the Liberian side of the border with Guinea and operates the railroad. The September deal, which ArcelorMittal said would extend its stay in Liberia by at least 25 years and at least triple existing production, has not been made public.
"We are concerned about the detailed conditions because what's important is not just theoretical access," de Selliers told Reuters in an interview.
"You can't invest $2.5 billion in a project in Guinea if you think you're constantly going to be hostage to the goodwill of someone else," he said, adding the company was in discussions with the Liberian government.
Liberian Mines Minister Gesler Murray said talks were going on with ArcelorMittal about usage rights for the railroad.
"The final agreement on another party using it is being finalised," he said. "We think it will benefit everyone."
An ArcelorMittal representative in Liberia was not immediately available for comment.
(Reporting by Aaron Ross; Additional reporting by Alphonso Toweh in Monrovia; Editing by Peter Cooney)
By Aaron Ross