Ireland is drawing up a claim for internationally recognised rights to huge tracts of the sub-sea continental shelf surrounding the country, according to the Department of the Marine.
As the technology for exploiting finds under the seabed in deep waters develops, Ireland could reap a substantial bounty in oil and natural gas, minerals and less valuable gravel, coral and sand deposits.
At present Ireland's right to the shelf out to a maximum of 200 miles is recognised internationally.
If successful, the new claim would mean an extension out to about 500 miles over some areas of the Rockall Trough and Hatton Basin under the Atlantic off the northwest coast.
A department spokesman said the extension would mean that the current 240,000 square miles of Irish continental shelf would increase by a third.
Ireland is among an estimated 60 states around the world that have substantial areas of continental shelf off their coasts that entitle the State to lodge a claim with the United Nations.
The new claim may lead to sub-sea territorial differences with neighbouring countries Iceland, the Danish-owned Faroe Islands and France.
An agreement on sub-sea borders has already been negotiated with Britain.