The PSNI and a gold mining firm are consulting lawyers in a dispute over security costs at a Co Tyrone site.
Police have billed Canadian multinational Dalradian almost £400,000 for escorting explosives but both sides are seeking legal advice and the sum remains unpaid.
Northern Ireland has the seventh richest undeveloped seam of gold in the world, the company has said. It hopes to submit an application for full planning permission before the end of the year and has already injected more than £56 million into the project.
Chief Constable George Hamilton said: “To date a total of £397,000 has been invoiced, however Dalradian are in disagreement with the chief constable’s position on cost recovery.
“Both parties are seeking further legal advice and this matter is with PSNI’s legal counsel. No monies have been received to date.”
Dalradian Gold plans to start digging under the Sperrin Mountains.
Around 3.5 million ounces of the precious metal had been identified at Curraghinalt near Gortin.
A spokeswoman for Dalradian Gold said: “There is a legal requirement in Northern Ireland for the PSNI to assess the need to escort the transportation of explosives. The form and manner of the escort is determined solely by the PSNI. We understand no other mining or quarrying operation in Northern Ireland pays for this service.
“Total investment into the project over the lifetime of the mine is expected to be in excess of hundreds of millions of pounds, creating hundreds of jobs in the process.
Environmental protesters have campaigned against the development but many local people are supportive after a community fund was established by the firm.
Gordon Best, spokesman for the Quarry Products Association Northern Ireland, said: “The idea that the PSNI will charge companies for escorting the transport and delivery of explosives to mines and quarries is a very troubling prospect for our industry.
“If this is applied, operating sites in areas that are deemed a higher security risk by the PSNI and therefore requiring a higher PSNI presence will have greater costs, and this could potentially create a regional imbalance for such extractive sites.
“Sites operating close to the border and therefore in possibly higher risk areas could become unviable and uncompetitive in comparison to their southern counterparts who are not subject to the same escort charges.
“Furthermore, many operators export their products into Great Britain and Europe and would face significant competitive challenges if these costs were to be applied.”