The Carter administration has abandoned its effort, begun nearly two years ago, to reduce the U.S. share of the Organization of American States' budget from two-thirds to one-half.

At the same time, in the continuing effort to cut the cost of what is considered a top-heavy OAS bureaucracy, the U.S. mission is opposing pay demands that have rallied the OAS staff association to the point of staging an unprecedented strike two months ago.

The staff association's president, Beatriz Lopez of Argentina, has accused OAS Secretary General Alejandro Orfila also of abandoning the interests of the 1,200 employees and has called for a response by Wednesday. The once timid association is collecting funds for a legal defense.

This conflict -- involving noncompliance with an OAS administrative tribunal decision that OAS salaries should have been on a par with those at the United Nations and ordered pay adjustments retroactive to 1976 -- comes at a delicate time for Orfila, who is seeking reelection at the annual OAS General Assembly next month.

While the Carter administration has supported the OAS, especially its human rights commission, the U.S. mission announced forcefully almost two years ago that the other nations of the 25-member organization should bear a larger part of the expenses. The overall budget runs about $80 million annually.

But the effort encountered intrasigence from the Latin American and Caribbean members, who argue that the U.S. ability to pay is far in excess of their own.

The U.S. mission has proposed that its contribution be reduced from 66 percent to 62 -- and even this cut would be at a rate of only one percent yearly over four years.

On the salaries issue, Owen Lee of the U.S. mission said that "the U.S. government is not too happy with the salaries in international organizations generally" and believes OAS salaries should be on a par with Washington's Civil Service. The U.N. scale runs about 10 percent higher.

Asked about the funding of the OAS administrative tribunal -- created with U.S. concurrence to adjudicate disputes for the otherwise unrepresented international civil servants here -- Lee suggested that the power of the General Assembly outweighed the tribunal.

Lopez said the staff association does not challenge the right of the General Assembly to set pay policy, but it could not retroactively cancel pay committed when it established parity with the United Nations in 1976.

The issue that emptied the new OAS headquarters for a day in July was that retroactive pay. OAS workers in the field reportedly supported the protest in large numbers.

With an eye to the U.S. position in the dispute, Lopez declared, "The countries are asked to respect human rights and respect the law. Why are they ignoring the rule of law in our case?"

The conflict follows other disputes indicating a restlessness within Washington's international bureacracy.

A group of former OAS employees has attempted to sue Orfila in U.S. District Court on matters involving their separation from the organization. At the World Bank, a group of workers has attempted to apply militant trade union practices to perceived job shortcomings. Workers at Washington's international banking institutions generally receive higher pay than the U.N. scale.