An effort to find a face-saving gesture for Arab nations that were defeated on a vote to get the Palestine Liberation Organization into the upcoming World Bank-International Monetary Fund meeting was under way last night.

American officials had won an all-out drive to keep the PLO out of the meeting, which starts here Sept. 30, fearing that Congress would cut off or sharply limit American funds for the two international lending institutions.

On the other hand, rich Arab nations such as Saudi Arabia and Kuwait have indicated they will cut off their support for the bank and the IMF if PLO is refused observer status.

But instead of claiming victory, U.S. officials slapped a tight embargo on news of the results of the resolution barring the PLO. A. vote of the 140 governors of the bank and the IMF was completed last Friday at 6 p.m. and went against the Arab bloc by what was described as a fairly close margin.

When the vote was in doubt, both sides had informed the two institution that they reserve the right to place the issue of PLO observer status on the agenda for the meeting itself. This would precipitate a public and probably acrimonious floor fight and, in effect, what the United States and its supporters have been trying to do since last Friday night is to discourage the Arab bloc from taking the question to the floor.

American officials have been trying to get what they call a negotiated settlement what would allow the forthcoming annual meetin to go about its main business, that is, seeking ways of helpong poor nations overcome their balance-of-payment difficulties.

But the face-saving settlement sought by the United States had not been achieved last night. An announcement planned by the World Bank for 3 p.m. was held up on a technical objection by the Arabs. Formal announcements may come from both institutions today.

One among several possible face-savers would be to bar all observers from this year's meeting pending a study of the entire question of observer status by a top-level committee of the bank and the IMF, which under the resolution adopted barring the PLO requires a report on the whole matter by next March 1.