TEGUCIGALPA, Honduras (AP) _ About 2,000 workers at the nation's only oil refinery today joined banana workers in a strike aimed at pressuring the U.S. banana giant Chiquita into paying higher wages.

Tens of thousands of other workers also threatened to join the walkout in what could be a crippling labor stoppage in this nation of 4.8 million people.

''The decision has been made,'' the president of the Texaco refinery workers' union, Roberto Zaldivar, said in a telephone interview. ''Today we begin paralyzing the refinery.''

Witnesses said workers had locked themselves inside the plant. At least 50 tanker trucks that normally would have been delivering gasoline to service stations were parked outside.

The Chiquita strike began Thursday and is the latest, and potentially most serious, labor unrest to hit the 5-month-old administration of President Rafael Leonardo Callejas.

Chiquita's 10,000 union members, including banana cutters, railway workers and administrative personnel, struck for a 60 percent salary increase, paralyzing operations. They now receive an average of $15.32 a day.

The 70,000-strong National Federation of Workers' Unions, which includes the Chiquita workers, said members of other unions would begin walking off the job today, starting with the Texaco refinery workers. The refinery supplies the entire nation.

Other labor groups, including the 600,000-member Workers Confederation, have said they will strike if Chiquita refuses to negotiate.

The president of the national legislature, Rodolfo Irias Navas, said the labor unrest could destabilize Honduras, the poorest nation in the hemisphere after Haiti with an annual per capita income of only $740.

''The crisis created by unionism is putting the stability of the government in danger,'' he said in a telephone interview.

Workers at Chiquita Brands International Inc. have not had a raise for six years. Inflation has climbed 50 percent annually, however, and their union asked the company for a higher pay in October.

Company officials calculated the raise would cost $4.6 million a year and had not made a counterproposal Thursday after four days of negotiating.

''The strike is illegal; it doesn't make sense. We aren't going to pay higher salaries to our workers,'' Chiquita Vice President Eduardo Aragon said in a telephone interview.

Company officials refused to comment further on the strike.

Bananas are Honduras' leading export and the Cincinnati-based Chiquita, formerly United Brands, is one of the most powerful institutions in Honduras.

President Callejas was trying Thursday to stop the strike from spreading.

He sent a high-level delegation to the northern coastal town of La Lima, headquarters of Chiquita, to mediate talks between union and company officials. He also kept in close telephone contact with union leaders, military officials and key advisers.

Callejas said he was sympathetic to the strikers, calling their demands for higher pay just. But he said there was no need for a strike.

''The unions are a fundamental piece of our democratic process,'' he said in a phone interview. ''But with me there is no need to strike because the unions can achieve their goals through dialogue, without resorting to force.''

About 4,000 health care workers have been on strike since June 11 to protest the privatization of support services in six of the nation's 19 public hospitals. Army troops are occupying the main hospital in San Pedro Sula, the nation's second-largest city, and army medics are providing emergency care.

Chiquita, which owns the country's only railroad, has enjoyed a near monopoly on the banana business in Honduras since 1912. It currently controls 60 percent of the bananas exported from Honduras. U.S.-based Castle and Cook controls the other 40 percent.