For the third time in four years, Continental Telephone Company of Virginia is mired in a tense labor strike that is disrupting service in parts of Northern Virginia and the southern end of the state.

More than 820 Continental employes represented by the Communications Workers of America (CWA) have set up picket lines from Woodbridge to Tidewater as federal mediators in Washington try to restart stalled negotiations.

Negotiations between union leaders and Continental representatives broke off Feb. 6 after the union rejected Continental's "final" wage and benefits offer, which company officials say would have totaled a 35 percent increase over the next three years. Union officials contend that increase would have been only 24 percent.

Since then, 300 strikers in Prince William County have picketed Continental offices from morning to night, often huddling around wooded fires in freezing temperatures.

More than 165,000 of Continental's 200,000 customers in Virginia are affected by the strike, which has caused interruptions in operator-assisted calls and a partial stoppage in phone installations and repairs.

Striking workers, all members of CWA Local 2275, an AFL-CIO affiliate, say they are primarily concerned about the wage and benefits package, although 21 contract issues, ranging from job transfer to honoring all union picket lines, remain unresolved.

Company and union officials say mediation talks are continuing this week, but neither side held much hope for an early resolution of the dispute.

Recently, the dispute has focused on company concerns about vandalism and union contentions that Continental has violated federal labor relations' laws.

Frank Casazza, Continental's vice president for personnel, said last week that 25 telephone cables have been sliced or damaged since the strike began. Continental officials also say that tires have been slashed on several company cars, and company parking lots have been laced with tacks. Company officials say they do not know who has caused the incidents. "But," said Casazza, "I find it more than coincidental that vandalism has dramatically increased since the strike began."

In response, Donnie Alvis, a strike coordinator for the union local and a Continental employe for 13 years, said, "There is a federal law against strike-related vandalism. We don't need to do this. The company has just been waiting for something to happen."

Alvis said he is more concerned by what he claims is harassment of workers on picket lines. Last week, union member Dennis Yankey said he witnessed an incident in which a nonstriking Continental employe aimed a car at picketers in front of Continental's Dale City office and looked as if he were going to run the picketers down. Prince William County police, who were notified of the incident, said no charges were filed.

John O'Connell, who is representing the union in federal mediation talks, said the union has filed one grievance with the National Labor Relations Board (NLRB) for alleged unfair labor practices by the company.

The grievance, O'Connell said, concerns a letter signed by William Dales, president of the company. The letter, dated Feb. 9, was sent to union employes, according to union officials. It read, in part:

"Employees who want to continue working may have to cross picket lines. Our lawyers have advised us that those of you who do this, while still a member of the union, may be subject to fines by CWA. In order to avoid such possible fines, all you need to do is resign from the union before crossing the line. Any such resignation will not and cannot affect your jobs in the future."

Continental Vice President Casazza said he had been told by the union that a grievance had been filed. By early this week, he said, he had not received the formal grievance notification and did not know what it entailed.

Officials at the NLRB District 5 office in Baltimore said a grievance was filed with their office Tuesday.

Meanwhile, union and company officials have adopted a hard line on negotiations. Both vow they will not surrender to the other side's demands.

"We're ready for the long haul," said Casazza.

"We're going to stay out as long as it takes to win," said an equally stubborn Alvis.

Union members have agreed to continue the strike until March 1, Alvis said. If there is still a stalemate by then, he said, the workers will reconsider their position.

For now, Alvis said, an AFL-CIO strike fund is paying strikers' bills for items such as food, utilities, rent and home mortgages. But until the strike is resolved, members of the union are not receiving their pay.

"The main thing we're worried about is the contract and the benefits," said Keith Garrett, 30, who is a strike coordinator.

Garrett, who has two children, said workers want more control over where they are assigned and also are concerned about benefits such as mileage allotments.

"We're worried about the future," Garrett said. "We're the baby boom. Who's going to take care of us when we're 66? Social Security is for the birds."