* Atlas, Flinders Mines could use Fortescue rail line
* Talks won't disrupt Fortescue port, rail stake sale
* Brockman awaits cost estimates from Fortescue (Adds Flinders Mines, Atlas Iron comments)
MELBOURNE, May 23 - Australia's Fortescue Metals Group is in talks with several parties interested in using its rail and port to haul iron ore, the miner said on Thursday, in a move to show it is ready to let rivals use its infrastructure.
If Australia's third-biggest iron ore miner opened its rail line, that would be a game-changer for several companies in Western Australia which have promising deposits but cannot afford to build multi-billion dollar rail lines to export their ore.
Fortescue announced the talks after responding to an application from one of the aspiring iron ore producers, Brockman Mining, that may force it to provide rail access at regulated rates.
It said it was holding commercial talks with a number of parties about port and rail access, separate from Brockman's formal application.
"We're pleased with the progress of these discussions and these will not be affected by the application," Fortescue said in an e-mailed statement, but declined to identify the participants in talks.
It said Brockman's application would not affect talks to sell a stake in its port and rail unit, the Pilbara Infrastructure (TPI).
Fortescue aims to sell a stake in TPI by the end of June to help it pay down A$3 billion to A$4 billion in debt as it looks to shore up its balance sheet in a volatile iron ore market.
Atlas Iron Ltd and Flinders Mines, which have said they were in talks with a range of parties to find ways to haul their iron ore to Port Hedland, both declined to say whether they were talking to Fortescue.
Robert Kennedy, executive chairman of Flinders, said it would consider following Brockman's route, applying for access under the state code within a few months, but added that it was preferable to hold talks with Fortescue, or the owner of the rail line.
"The first thing one should do is discuss it with them. That's a much better way," Kennedy told Reuters. "We've got no need to be aggressive about anything. We're not going to achieve anything that way."
Kennedy said the outcome of the sale of a stake in TPI was being closely watched by the industry, as it would show whether Fortescue would allow an independent operator to run the rail and port, a step towards easing access for others.
Until now, Fortescue has said it does not want to give up control of its rail line and was looking to sell a stake of only around 40 percent in TPI.
Brockman is awaiting Fortescue's response on cost estimates for different sections of its rail operation, which the state will study as the basis for regulated rates.