A Canadian firm that wants to develop a mine near Omagh, County Tyrone, has said it has had to put its plans "on hold" and that jobs could be lost.
Galantas Gold says it could not get the necessary "anti-terrorism cover" from the PSNI for its blasting operations.
The police are required to provide the cover for the transportation and use of mining explosives in Northern Ireland.
The PSNI said there were "many competing demands" for the resources of the police.
Background - John Campbell, BBC News NI business editor
The PSNI normally escort explosives when being brought to a quarry or mine in Northern Ireland.
There will also be an explosives officer there during blasting. Their job is mainly about auditing the use of detonators - how many have been used, have the excess detonators been disposed off etc.
This is something that has been happening for 40-plus years.
But a typical quarry blast would only happen about twice a month.
In a gold mine, explosives use is much more intense - blasting happens three or four times a week. Hence the police are saying it is a resource issue for them.
According to Galantas, the PSNI said it could only provide anti-terrorism cover for a two-hour period, two days a week.
This would not be enough to sustain development or operation of the mine, said the company.
It is now threatening to sue the PSNI saying it may seek "substantial compensation for the costs of delays".
Roland Phelps, the chief executive, said: "The PSNI's decision is clearly a blow to any proposed mine development in Northern Ireland and negatively affects the livelihoods of our employees and their families."
PSNI Ch Supt Kevin Dunwoody said the police must prioritise demands "in a way that maximises the safety of the public and their officers and works to counter threats, to mitigate risk and to alleviate harm".
"Working with others to support their efforts for the development of enterprise and the economy is important to the PSNI," he added.
"It is, however, reasonable to expect a commercial venture to contribute all or part of the policing costs where it is legitimate and proportionate to do so."
Galantas have emphasised they were willing to enter into a "cost-recovery arrangement" with the PSNI but were told there was no manpower available to provide the cover.