The caller was on hold, waiting for a number, and Margaret Fletcher, a phone company secretary turned temporary directory-assistance operator, was trying to clear her computer display screen in order to call it up, when suddenly the line went dead.

Fletcher looked down and realized she had accidentally hit the disconnect button. "I just said 'Oh goodness, I lost the customer,' " Fletcher, an employe of the Chesapeake & Potomac Telephone Co., recalled later. "They were gone. What could I do?"

Similar accidental cutoffs and delays in operator-assisted and directory-assistance calls continued yesterday as the nationwide telephone strike of nearly 700,000 employes went into its second day. Most calls went through smoothly, however, since 97 percent of all calls are dialed directly by telephone users, according to spokesmen for the American Telephone & Telegraph Co.

Top officials of the Communications Workers of America, which represents 525,000 of the striking workers, and of AT&T both reported no serious negotiations and no progress yesterday in attempts to settle the walkout.

A spokeswoman for AT&T said the company was "waiting for a call from the union. We're expecting bargaining to start."

CWA president Glenn E. Watts said he too would like negotiations to begin, but "unfortunately, I cannot report any progress is taking place."

Watts, who briefly joined a picket line in front of a C&P office here, repeated that the union is prepared for a lengthy strike. "Obviously we always hope that we can bring a settlement about in a short period of time," Watts added.

Watts acknowledged that strikers could not shut down the highly automated phone system, which is relying more and more on advanced and rapidly changing telecommunications and computer technology. But, he said, "You can't really say that when 700,000 people leave a business . . . it's going to operate as normal. All kinds of disruptions take place internally."

Job security, particularly the retraining of telephone workers who are replaced by the technology, is a major issue in the strike along with union requests for better wages. In the Washington area, alone, a union spokeswoman said, the number of operators has shrunk from 4,000 to 1,500 in the last decade.

The company has agreed to some retraining and has offered wage increases for some workers of up to 3.5 percent in the first year of a proposed three-year contract, followed by cost-of-living adjustments in the next two years. The union wants the company to more than double its proposed wage increase.

Pickets were thrown up at telephone offices around the country, including the Washington area offices of C&P, which has 11,500 unionized employes out of more than 14,000 in its total area work force, which includes the Virginia and Maryland suburbs. The picketing also extended to the White House, where about 10 union members marched.

A small army of telephone company management and supervisory personnel have been called out across the country to fill in as operators, repairmen, phone installers and at a variety of other positions. In the Washington area, C&P is relying on between 2,500 and 3,000 management and supervisory workers to do the jobs normally performed by the 11,500 union employes.

People making long-distance directory assistance calls to some parts of the country, including San Francisco, Atlanta and Baltimore, were sometimes greeted with a recording, saying "Sorry, all circuits are busy."

C&P is continuing to perform repair and installation work but priority is being given to emergencies, such as homes or companies without any phone service or breakdowns at essential government agencies. Similar policies on repairs and installations were in force around the country.

The strike began at 12:01 a.m. Sunday when the previous three-year contract expired and negotiations between the company and union officials had failed to lead to an agreement on a new contract. Unions joining CWA in the walkout are the International Brotherhood of Electrical Workers, with 100,000 members, and the Telecommunications International Union, representing 50,000 employes.

In the Washington area, R. Webster Chamberlin, spokesman for C&P, said the system was operating without any major problems. "There are some customers that are waiting out there, there's no question about it," Chamberlin said.

He said the important thing was that directory-assistance and operated-assisted calls were being handled and delays were minimal. "We're not trying to measure the delays," he said.

According to Naomi Gudger, a directory assistance supervisor at one C&P location, her unit normally averages 1,700 to 1,800 calls a half hour. Yesterday, she said, during that same time period, about 1,100 calls were processed.

Blondell Stewart-Ware, president of CWA's Local 2300, which represents the operators in the Washington area, said it was natural for company officials to paint a rosy picture. "But the system is suffering," Stewart-Ware said.

Back at the directory assistance center at 722 12th St. NW, a weary Fletcher, who had been on the job since 6 a.m., said her confidence increased during the day and that while it had taken her longer than a normal operator, she had made few mistakes.

Still, said the 10-year phone company veteran, she found that being an operator can be "very boring and tiresome. It's hard on the eyes and the back . . . . You almost feel like a robot."