Norway's offshore oil production, the country's most important industry, has been halted by a strike by 3,500 oil workers on the giant rigs in the Norwegian sector of the North Sea.

The strike is costing nearly $35 million a day in lost oil revenue according to the Norwegian government, which is losing the nearly three-fourths of that money it normally collects in royalties and taxes.

The strike began last week when 2,000 production and maintenance workers employed by the Phillips, Mobil and ELF oil companies in the major Norwegian oil fields in the North Sea stopped work in a dispute over wages and hours. They want big pay raises, a shorter work week and earlier retirement, which the oil companies claim would add up to nearly a 100 percent increase in wage costs.

This week, another 1,500 workers went on strike, abandoning work on the Mobil oil rigs that drill exploration wells in the Norwegian sector. They are demanding 30 percent increases in pay.

It was the first time that Norwegian oil production has been stopped in more than a decade of drilling in the North Sea, and the first time that the oil companies have presented the workers with a united bargaining front. Government, industry and union officials see no sign of a comprise settlement soon.

The strike also has important wider implications for the Norwegian economy and labor relations. Earlier this year, the rest of Norway's workers agreed to a new, two-year national wage agreement with the country's employers. a

To help hold down inflation after a successful 15-month wage and price freeze that ended in December 1979, the workers agreed to wage increases averaging just over 5 percent a year, with larger raises for the lowest-paid workers. Union leaders hailed this an important act of labor solidarity by higher-paid workers, who would get lower raises.

But the 2,000 oil workers on the Phillips, Mobil and ELF rigs in the North Sea, who had organized themselves into one of the few unions outside Norway's umbrella trade union organization, decided they would not be bound by the national wage settlement. Already among the highest paid skilled workers in Norway, they want much bigger pay raises and other benefits than they would have gotten under the national agreement. This amounts to a rare and potentially damaging break from the traditional Scandinavian welfare state pattern of centralized labor negotiations.

If the striking oil workers get what they want from the oil companies, Tor Helvorsen, chairman of the national Trade Union Congress, warned this week, the rest of the nation's workers must get the same deal. He said that it would be "unacceptable" to open a gap between his organization's members and the offshore oil workers.

This has created a dilemma for the Norwegian government, which is reluctant to use its power to call in a compulsory arbitration committee to settle the dispute. It might award the oil workers so much money, because the oil companies can afford it, that the national wage agreement would be undone.

In addition, Prime Minister Odvar Nordli's Labor Party government depends on support from the traditional labor unions, whose members and leaders have become increasingly resentful of the independence and high pay of the offshore oil workers. Nordli said his government would keep a close watch on the strike and could decide on compulsory arbitration "at any time if the situation requires it."

Meanwhile, the striking workers have remained on the oil platforms to prevent the oil companies from bringing in others to run the rigs. They have agreed to maintain necessary safety measures.

Although this week's additional strike of workers on exploratory drilling rigs also affects six such rigs in the British sector of the North Sea, Britain's oil production is otherwise unaffected. Very few of its more numerous offshore oil workers are unionized, and they have never called a similar strike shutting down production.