The nationwide strike against the government of President Anastasio Somoza Debayle began its third week yesterday, as most workers continued to stay home despite attempts by businessmen to reopen shops, offices and factories.

Many gathered outside their work places in Managua this morning to persuade colleagues to continue striking. A number of clashes were reported between workers and combat-dressed National Guard troops who toured the streets in open jeeps and ordered people back on the job.

Meanwhile, a source close to Somoza said the president "feels the heat is off," and that the strike has collapsed for "economic reasons."

He appearnently was referring to the decision of the country's leading business federations over the weekend to end two weeks of organized shutdowns, and let individual companies decide whether to open.

At starting time yesterday morning, many of the businessmen, a number of whom reportedly have continued paying their employees during the strike, found the workers willing to continue striking on their own.

"No one wants to go to work," said the manager of a locked dress shop who gathered with other employees at one of Managua's largest shopping centers. "We will stay on strike until we win. We will died frm hunger first."

Among the few stores open in the shopping center were a Somoza-owned television concern and a branch of the Bank of America.

"We don't want to work," employees in the bank said. "We're very nervous. But the bank asked us to, otherwise they would bein trouble with the government."

The strike began two weeks ago, sparked by the Jan. 10 slaying of opposition leader and publisher Pedro Joaquin Chamarro on a Managua street. With business support, it quickly spread to include the shutdown of more than 80 percent of the country's businesses. The strikers accused Somoza of complicity in the murder and have demanded his resignation.

Somoza, whose family has controlled Nicaragua for about 40 years, has been accused by international rights organizations of human rights violations against the country's peasants and of maintaining virtual martial law through the National Guard.

Following decades of support for Somoza, the United States under the Carter administration has cut assistance to Nicaragua and has maintained a strict hands-off policy during the current crisis.

In a meeting with businessmen Saturday, U.S. ambassador Mauricio Solaun reportedly emphasized nonintervention, clarified the aid situation and confirmed local press reports that the Somoza government has hired several American mercenary soldiers.

Early today, a group of 12 women involved in a sit-in strike at the United Nations Development Fund office here agreed to go home following negotiations with the government guaranteeing their safety.

William Baez, executive director of the Nicaraguan Development Institute, a federation of about 700 businessmen, called the strike a "tremendous success" and said the business sector supported the workers, despite the decision of many to reopen after "making our point clear" for two weeks.

"Somoza claims this is a rich people's strike" because the businessmen could afford a two-week shutdown, Baez said. "Well, now the businesses are open and people are not going to wor."

Last week, four of Nicaragua's independent radio stations shut down when reporters protested an emergency ban on news of the strike. Reporters now gather at their union headquaters, and compile strike news to be read at churches around the country at daily mass.