Saudi Arabia's pledge to the proposed multibillion international loan fund for financially pressed nations is likely to be smaller than the $4 billion sought by major inustrial nations, according to Saudi Finance Minister Muhammad Aba Khayl.

Khayl, who is here to confer with Treasury Secretary Michael Blumenthal and other officials, said in an interview that a $4 billion allocation is "not realistic". He would give no estimate of the money his government is likely to make available, but said the decision will be made within two or three weeks.

The size of the Saudi pledge is crucial to the massive financing plan being worked out under the auspices of the International Monetary Fund. Since sponsors hope for a loan kitting provided half by oil-producing countries and half by industrial states, a Saudi contribution of less than $4 billion would create a total fund far lower than the $14 billion to $16 billion which was originally sought.

Saudi Arabia, with its very large oil revenues and foreign exchange surplus, is expected to provide the lion's share of the funds provided by oil-producing nations. The money would be made available to the IMF as a loan at prevailing market interest rates.

Late last week IMF Managing Director H. J. Witteveen reaffirmed an eventual target of $16.5 billion for the fund to assist nations in financial trouble. But he also set out an initial target of $9.5 billion the first year, evidently in reaction to soundings with the Saudis and other nations. Even the initial target might be difficult to reach if the Saudi pledge is less than $4 billion.

Explaining the Saudi position, Khayl said, "We have to take into consideration our previous loans to the IMF, our commitments to developing countries and our situation as a developing country ourselves."