According to the paper, BSG Resources Chief Executive Asher Avidan is in Brazil looking for legal advisers, with a view to filing a lawsuit against BTG Pactual and partner AGN Participa??es. BTG Pactual and AGN created holding company B&A Participa??es to invest in mining projects globally.
Avidan is concerned that BTG Pactual's role as an adviser to Guinea's government could help B&A win license rights at the expense of the BSG-Vale venture, Estado said.
He was quoted by Estado as saying: "BTG and Agnelli are trying to sneak in through the back door. They are negotiating directly with Alpha Mohamed Cond?," Guinea President Alpha Cond?'s son.
Vale and BSG operate in a portion of Guinea's Simandou development, which is thought to be the world's biggest untapped iron ore deposit. Estado cited BTG Pactual executives as saying that the bank's advisory to Guinea's government covers just a portion of Simandou and not all, as Avidan claims.
BTG Pactual did not have an immediate comment when contacted by Reuters. A spokeswoman for Vale did not comment on the Estado report. Reuters' efforts to reach AGN Participa??es and BSG Resources executives for comment were unsuccessful.
AGN Participa??es is controlled by Roger Agnelli, the former CEO of Vale. Agnelli left Vale last year following a clash with Brazil's government, a key Vale shareholder, over strategy.
Guinea, the world's top bauxite supplier, is locked in disputes with mining firms over control and ownership of mining projects. The government says more state control of mining could help combat poverty in a country that has struggled with decades of conflict since independence from France in 1958.
Cond? wants to insert a provision to take the government's share in mines from 15 percent up to 35 percent, the first 15 percent of which is free. Simandou is in the spotlight at a time when mining companies are holding up spending and ore prices are falling.
Last month, a clash between security forces and villagers in Zogota, where Vale and BSG Resources operate, left six people dead. Both companies plan to start output at Zogota this year.
The mine is designed to produce up to 15 million tonnes of ore a year. Vale, which bought a majority stake in the project from BSG in 2010, hopes to boost output to 50 million tonnes a year by 2020.