Robert Muldoon is currently prime minister of New Zealand, not the former prime minister, as reported yesterday in the Business & Finance section. Muldoon is a former chairman of the board of the International Monetary Fund and the World Bank.

Saudi Arabia's commitment to lend the International Monetary Fund $10 billion over the next two years, with more possible in a third year, is not likely to be affected "at all" by the IMF's decision Monday to ban the Palestine Liberation Organization from its 1981 annual meeting in Washington, according to unofficial but informed views.

The PLO has been branded as a terrorist organization by the United States, which for two years has vigorously been pressing a campaign to keep the Palestinians out of the IMF-World Bank sessions. The World Bank on Friday ruled against observer status for the PLO.

There are no immediate Arab loan relationships that loom as a complication for the World Bank, officials said.

Sources at both the IMF and Bank said yesterday that the Reagan administration, even more sternly opposed to the PLO than was the Carter administration, won its case with surprisingly little active opposition from the Arab side. And in fact, by deciding to limit observers to those who attended the 1979 joint meetings in Belgrade, the PLO effectively has been shut out of the 1981 sessions without having to resort to a total ban of other observers, the device evolved by the Carter administration at the 1980 sessions in Washington.

"I get the feeling that the Arab nations feel there are other more important issues in the Middle East and that the PLO is regarded as a secondary issue," said one IMF source. It was pointed out tht the chairman of the joint 1981 sessions -- who technically issues the invitations to observers -- is scheduled to be a Uruguayan, likely to be less sympathetic to the PLO cause than was last year's chairman, Tanzanian Finance Minister Amir Jamal.

Jamal last year extended an invitation to the PLO, which had begun its so-far unsuccessful campaign in 1979 at the Belgrade sessions. But Jamal was overruled at the top levels of the Bank and IMF, which referred the matter to a committed headed by former prime minister of New Zealand Robert Muldoon.

According to the Locally published Middle East Policy Survey, Secretary of State Alexander Haig on May 19 addressed a letter to foreign ministers in Europe and Canada, urging their support of the U.S. anti-PLO position. Haig was quoted by the survey as arguing that "issues relating to the PLO can properly be addressed only in the context of negotiations for a Middle East peace."

Haig's letter warned that "there can be no compromise" on the issue, adding that President Reagan personally had expressed opposition to admittance of the PLO, fearing that Congress would trim back financial support for international institutions if the PLO did gain observer status.

Haig had the strong and active support of Treasury Secretary Donald Regan and Treasury Undersecretary for Monetary Affairs Beryl Sprinkel.

Last year, led by Libya and Kuwait, the Arab members of the IMF and World Bank struggled hard against the determination of the Carter administration to keep the PLO from attending the sessions, which took place in Washington. After some bitter exchanges. The PLO was barred only by a gimmick that kept all observer organizations out of the sessions, avoiding the substance of the issue.

A World Bank source suggested that the Arab leaders, notably Saudi Arabia's representatives, feel that they have argued the PLO case as forcefully as possible, and that it can be revived whenever there is a propitious time to do so. Saudi Arabia's new permanent seat on the executive boards of the two institutions, it is believed, places it in a stronger position to argue the case for the PLO later on, if it chooses to do so.