The International Monetary Fund yesterday announced a package deal with Saudi Arabia which vastly increases the Arab nation's power and prestige within the lending agency and at the same time commits it to lend the IMF approximately $10 billion over the next two years.

Paying tribute to the Saudis for their prompt response to the IMF's needs, IMF Managing Director Jacques de Larosiere said that the deal recognized the importance of Saudi Arabia "in the real world" and will enable the IMF to continue lending to poor countries without interruption.

Coincidentally, de Larosiere said the IMF is pursuing an effort to borrow $1 billion or more from the stronger industrial nations and is also still completing negotiations with Kuwait and the United Arab Emirates for additional loans. He estimated that the new Saudi commitments will cover only about two-thirds of the extra money the IMF will need over the next three years.

By doubling the Saudis' quota (or deposits) in the Fund from 1 billion Special Drawing Rights (SDR) to 2.1 billion SDR, the Saudis' voting power is increased roughly to 3 1/2 percent, which automatically gives them a permanent seat in the IMF Executive Board. They now rank sixth, instead of 13th among the 141 nations in the IMF. (The SDR, the IMF unit of account, is worth about $1.22.)

As a consequence of the enlarged Saudi quota, all other nations will share a fractional decline in their percentage relationships. The U.S., for example, will drop from approximately 21 percent to 20.78 percent of the total quotas. But the IMF Executive Board vote on the package was unanimous, and de Larosiere said that the United States had played an important part in the whole negotiation. "We found the U.S. attitude most constructive and cooperative," de Larosiere said.

The deal with the Arabs, which de Larosiere has been trying to pin down more than a year, comes at a time when the IMF is fast running out of useable hard currencies to meet growing demands on its resoures. Until the new infusion of money was announced, the IMF could count on useable hard currencies of barely 21 billion SDRs, which meant that its bank account would be exhausted at the present pace in little over a year.

IMF loans have been booming to meet the needs of its hard-pressed members, fighting off the effects of rising oil prices and recession in the industrial world. In 1979, for example, total loans had been only 2.2 bilion SDRs, the equivalent of $2.7 billion. Last year, that figure rose to 7.2 billion SDRs, or $8.8 billion. In the first two months of 1980, the annual lending rate has been close to 17 billion SDRs, or more than $20 billion.

The Saudis agreed to lend the IMF 4 billion SDRs in each of the first and second years of the agreement and promised additional loans in a third year if their financial situation permits. Interest will be paid on a basis of market rates in the five largest countries, with the average term of the loan to be 5 1/2 years.

There are some unique features to the loan arrangement, made through the Saudia Arabian Monetary Agency (SAMA). Notably, it contains an option for the Saudis to convert their claims on the IMF into bearer notes that would be transferrable to other public or private parties.

A complicating factor in persuading the Saudis to lend additional funds to the IMF has been a running dispute over the Palestine Liberation Organization. For the past two years, the PLO has sought observer status at the joint annual IMF-World Bank meeting, but American opposition has kept the PLO out.

Most other industrial powers, notably West Germany, have long argued that such recognition for the wealthy Saudis is long overdue, in both the IMF and World Bank.

De Larosiere said that the PLO question had not entered into the negotiations, which were "strictly financial." But according to informed sources, the Saudis feel they will be able to argue the PLO case more effectively now that it is entitled to a permanent seat on the Board by virtue of its paid-in quota, not simply because it is one of the two largest lenders to the institution.