Russian President Dmitry Medvedev and Norwegian Prime Minister Jens Stoltenberg said only technical details remain to be worked out before a deal can be signed delimiting the border, ending negotiations that have dragged on for decades. Such an agreement would also have to pass the two countries' legislatures.
"We have now turned the page on this issue," Medvedev told reporters in Oslo, adding the disputed area was "divided in a fair way."
NATO member Norway and Russia failed to agree on a maritime border in the Barents Sea during the Cold War and couldn't reach a deal despite several attempts following the 1991 collapse of the Soviet Union.
Some 90 billion barrels of oil and one-third of the world's undiscovered natural gas lie hidden in the Arctic region, the U.S. Geological Survey estimates. Both Medvedev and Stoltenberg noted that the latest agreement would promote cooperation between the two countries' energy sectors.
Stoltenberg said the countries have now reached "a good and balanced agreement." He said Russia and Norway would get "more or less equally sized pieces" of the disputed 68,000-square mile (175,000-square kilometer) area and that Russian officials told him they could be ready to sign a finalized agreement later this year.
Following the announcement, Norwegian Foreign Minister Jonas Gahr Stoere and his Russian counterpart, Sergey Lavrov, signed a joint declaration outlining the preliminary agreement.
After 40 years of disagreement, experts on Norway-Russia relations had downplayed the likelihood of an agreement ahead of Medvedev's state visit to Norway.
"I wouldn't have expected a deal. It's so difficult for countries to give anything up," said Indra Oeverland, a Russia expert at the Norwegian Institute of International Affairs. "It's a big step forward."
Interest in the Arctic region is intensifying as global warming shrinks the sea ice that blocks shipping and oil exploration.
The two countries have already begun developing the natural resources buried beneath the floor of the Barents Sea.
The Norwegian oil company Statoil brought its Snoehvit natural gas field on line in 2007. Meanwhile, Russia's Gazprom, in conjunction with Statoil and France's Total, is developing the Shtokman gas field, although the project has been plagued by repeated delays.
Oeverland said if the Shtokman project became successful it could "operate as a sort of template" for Norwegian-Russian resource cooperation in the area.
News of the deal was met with mixed reactions from environmental groups, who fear new oil exploration and development will increase pressure on the fragile Barents Sea ecosystem.
"With a clearly defined border, at least we'll know what we're going to be dealing with," said Fredric Hauge, who leads the Bellona Foundation, a Norwegian environmental group that also works in Russia.
Meanwhile, Stoltenberg was reluctant to talk about Norway's plans for whatever resources the region might yield.
"It's not clear yet when we will be able to begin developing the resources in this (disputed) area," he told reporters later Tuesday. "We have to wait for the agreement to be finalized."
World media monitoring