OSLO -- Norway can afford to say "No" to joining the European Union because its economy is fueled by huge oil and gas revenues.


But it could cost jobs and scare off investment if Norwegians turn down membership in Monday's referendum.


With neighboring Sweden, Norway's biggest trading partner, and Finland inside the EU from next year, many firms may face tough competition if Norwegians choose to stay outside.


"I don't think a 'No' will be dramatic for Norway in the short run, but it could be serious in the longer term as it could make Norway a less attractive investment area," said Knut Kjaer, a researcher with the independent Econ institute.


While one opinion poll published Friday indicated that the "Yes" side is ahead for the first time, two others show the "No" side increasing its lead, suggesting that Norwegians might go for self-imposed isolation on the northern fringe of Europe.


The core of the protests against EU membership come from farmers afraid they might lose lavish subsidies and fishermen worried about competition from EU trawler fleets in Norwegian waters.


Oil and gas revenues, which represent some 33 percent of export earnings, have made it possible for Norway to keep some of the highest farm subsidies in the world.


Many brokers say the stock market might drop and short-term interest rates rise should Norway reject membership and there is a lot of market uncertainty ahead of the referendum, but no-one expects an economic slump in the wake of a rejection of membership.


Central Bank governor Torstein Moland believes a no-vote has to a great extent been priced into the bond and currency markets.


The economy is booming, with total growth forecast at 4.5 percent this year and 2.75 percent in 1995. Unemployment is relatively low, seen at 6 percent this year. But a recent study by the Confederation of Norwegian Business and Industry forecasts that industry could lose an estimated 100,000 jobs over the next four years if Norway decides to stay outside the trade bloc.


The study said the situation would be especially dramatic for the forestry, car spares, chemical, manufacturing and fishing industries.


Companies fear they will suffer from poor market access and disadvantageous import duties for salmon and other products as well as a lack of influence on decision-making in Brussels.


"Both Swedes and Finns have secured a huge domestic market and direct opportunities to influence (decision-making)," said Jan Reinaas, president of Norway's biggest forestry firm, Norske Skog, which depends on EU nations for almost half its earnings. "Norwegian forestry industry will be in a weakened position compared to its competitors if Norway stays outside," he warned.


The "No" side argues that Norway will still have access to EU markets through the European Economic Area Agreement, or EEA, between the EU and the European Free Trade Association.


But many fear that the EEA accord will be weakened and probably have to be re-negotiatated now that trade association members Austria, Finland and Sweden are joining the EU.


They also expect future investments to be channeled elsewhere if Norway chooses to stay outside.


Norway has in its membership deal secured sovereignty over its huge oil and gas resources, and membership would likely have little effect on the oil sector.


But Industry and Energy Minister Jens Stoltenberg and others argue that Norway, which exports nearly all its gas to Europe, would benefit from joining the EU as membership would give Oslo a say in the future market regime for gas.