OSLO (AFP) - The leaders of Russia and Norway said Tuesday they had agreed on a compromise Arctic border in the resource-rich Barents Sea, bringing an end to a 40-year dispute.

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"This solution is about more than a border line under the ocean. It is about developing good neighbour relations," Norwegian Prime Minister Jens Stoltenberg told a joint press conference in Oslo with Russian President Dmitry Medvedev.

"It will unite much more than divide, and it will become a bridge to cooperation," he added.

Since 1970 Norway has been in dispute with first the Soviet Union then Russia over a 176,000-square-kilometre (67,950-square-mile) maritime area straddling their economic zones in the Barents Sea and the Arctic Ocean.

The surprise compromise reached during Medvedev's state visit plans for the contested zone to be divided almost equally between the two countries.

It will allow both Norway and Russia to chart the maritime depths of the ocean with the aim of discovering potential oil and natural gas reserves.

The territorial dispute has been the main source of discord between the two countries for the past 40 years.

"I am glad that we have turned this page ... If problems are not solved definitively then there is friction which presents a strain," Medvedev told the press conference.

"This is a big event in Norwegian-Russian relations and for Europe and as whole," he added.

Rivalry over the Arctic riches has heated up as melting polar ice and new technologies have made the region more accessible.

Canada, Denmark, Norway, Russia and the United States are at odds over how to divvy up the Arctic seabed, thought to hold 90 billion barrels of oil and 30 percent of the world's undiscovered gas resources, according to the US Geological Survey.

The five countries vowed in 2008 to resolve territorial disputes through negotiation and balance economic opportunities with conservation of this fragile ecosystem.

Yet each has also been beefing up its military presence in the region.

Three Arctic countries, Canada, Russia, and Denmark -- which is present in the Arctic through Greenland -- claim the North Pole as their own, a dispute highlighted in 2007 when a Russian mini-submarine reached the bottom of the Arctic Ocean under the North Pole and left a Russian flag.

Disagreements even persist between close allies: Canada and the United States are at odds over the Northwest Passage, which Ottawa claims as its own but the US considers to be in international waters; and Denmark and Canada are bickering over who owns the deserted Arctic isle of Hans.

The Norwegian-Russian accord shows that Norway and Russia are not conducting a policy centred on the rush for resources or on rivalry, but one centred on cooperation," Stoltenberg said, stressing the agreement was based on international maritime law.

"This will lead the way to cooperation in many fields, particularly in energy," Medvedev said.

There are already several large projects underway to pump up vast fields of oil and natural gas outside the area split by Tuesday's agreement.

Russia plans to exploit the massive Shtokman gas field in its zone, while on the Norwegian side, the Snoehvit gas field is already on line and the Goliat oil field is being developed.

The signature of the accord is still subject to technical details, which both sides said they would work to resolve rapidly.