Among President Jose Napoleon Duarte's headaches in the current election campaign is the mystery of the $150,000 of U.S. support funds that never arrived.

Two senior officials of the U.S. government-funded American Institute for Free Labor Development told Salvadoran union leaders in January and last month that an unidentified person would come from the United States in early March with $150,000 for them to help Duarte's campaign, seven union leaders said in on-the-record interviews.

But the money was held up because the institute was unhappy with Salvadoran resistance to the formation of a new national labor confederation that would be independent of partisan politics -- unlike an existing, Duarte-allied trade union alliance -- the labor leaders said.

In last year's presidential elections, Salvadoran unions received $200,000 for Duarte's campaign, including money to pay salaries of hundreds of union activists who canvassed house-to-house, union leaders said.

The CIA reportedly funneled between $1 million and $2 million last year to help Salvadoran political parties, notably Duarte's Christian Democrats.

The American Institute for Free Labor Development's regional director for Central America, Roberto Cazares, and its recently transferred former Salvadoran director, Bernard Packer, were the two officials who discussed the $150,000 of funds this year, the union leaders said.

"They told us that a person from the United States was going to bring us funds for the campaign," Salvador Carazo, chief of the new confederation, said.

"Mr. Packer told us that someone would come, . . . but not from the institute," he added.

Institute spokesman Jack Heberle in Washington quoted Cazares as denying that he made such an offer.

Heberle said that it was "hardly likely" that any institute official did so, because the institute was not providing money for Salvadoran campaign activities.