Leaders of a staff association representing 1,000 employes of the Organization of American States here have called for a one-day work stoppage today to protest the organization's failure to keep salaries on parity with United Nations employes.

Beatrice Lopez, a translator and chairman of the OAS Staff Association, said the pay of OAS professionals and clerks has fallen about 20 percent behind United Nations employes since 1976 when the OAS officials declined to grant cost-of-living raises given to U.N. employes.

Most of the association members are professionals who earn about $20,000 a year , Lopez said. Nonprofessional members earn more than $10,000 a year, she said.

The pay dispute dates back to 1970 when the OAS agreed with association to maintain pay party with the U. N. association members said. In 1967, the OAS officials dropped partity, the members said. The association appealed in 1978 to a special tribunal of OAS member states, which, according to Lopez, ruled that the employes were entitled to the raises.

Alejandro Orifila, secretary general of the OAS, which represents 27 Latin American countries and the United States, was in Bolivia yesterday and unavailable for comment. Lopez said the work stoppage would interrupt planning for the OAS meeting scheduled for October in Bolivia.

Lopez said that instead of striking, the members were asked to take a day of annual leave. It would be the first such work stoppage in OAS history, members said. The organization was formed in 1889-90 as the Union of American Republics. Its name was changed to the Pan American Union in 1919 and it became the Organization of American States in 1948.