Oil companies have begun looking for crude deposits off the west coast of Greenland, and Joern Skov Nielsen, deputy director of Greenland's Bureau of Minerals and Petroleum, said there may be more oil there than the entire past production of the North Sea. That's about 50 billion barrels, according to figures from Norway and Britain, the region's biggest producers.

At $US100 a barrel, that would be $US5 trillion worth - a potential windfall for the autonomous Danish territory's 56,000 inhabitants that may start paying off in about 15 years.

''This is an epoch-making time, and how we handle it will be of colossal significance,'' said Aleqa Hammond, Greenland's Minister of Foreign Affairs and Finance. ''Greenland will be a player in the global arena in many more ways than we can even begin to imagine.''

While geologists have known that Greenland had crude reserves since oil was discovered seeping out of rocks along the coast in the 1990s, the ice surrounding much of the world's largest island made getting to it unfeasible.

With crude prices up 63% in the past year to about $103 a barrel and the ice melting, the reserves have become potentially more lucrative.

Last October, Greenland's government awarded exploration licences to Chevron, Exxon Mobil and Husky Energy. The companies are collecting seismic data to determine the best drilling sites.

Given the icy conditions, oil production may cost as much as $US46 per barrel, according to Oil and Gas Journal. While exploration is complicated by icebergs as tall as 15-storey buildings, global warming is helping.

Outside the Disko Bay area off the west coast, there were on average 180 ice-free days a year between 2000 and 2005, up from a 25-year average of 150 days, said Leif Toudal Pedersen, a spokesman at Denmark's Meteorological Institute.

''If the ice in west Greenland continues to melt as dramatically as it has been doing in the past few years, then the cost of producing a barrel of oil will be closer to $20 than $50,'' Nielsen said.

There may be even more oil off Greenland's north-east coast, where the US Geological Survey last year reported a possible 31.4 billion barrels. That area is more desolate than the west coast; the largest nearby town is Illoqqortoormiut, population 529.

Those reserves would represent a greater challenge because the water freezes into pack ice that can be 3 metre thick and thaws enough to allow ships through for one month a year at most.

Though global warming may make that oil accessible at some point, ''the technology actually doesn't exist'' yet to explore through the ice, said Hans Kristian Olsen, chief executive of NunaOil, Greenland's state-owned oil company.