The United States yesterday brusquely rejected a formal complaint lodged with the International Monetary Fund that it illegally had blocked Iranian assets and in doing so had undermined "the world confidence in the international banking system."

In a speech to the joint annual meeting of the IMF and World Bank -- which concludes today -- E. Rashidzadeh, temporary alternate IMF governor for Iran, denounced both the United States and the IMF. He attacked the U.S. for its action on November 14, 1979, and the IMF for failing to endorse its earlier complaint about the freeze.

Meanwhile, another tendentious issue -- the question of admission of the Palestine Liberation Organization -- was referred by a Joint Procedures Committee to a special commission of governors of the two institutions to examine the question of whether the temporary exclusion of the PLO at this meeting was in accordance with the bylaws.

Countries represented on this commission are: Belgium, France, West Germany, New Zealand, Sweden, Indonesia, Pakistan, Nigeria, and Yugoslavia.

Treasury Secretary G. William Miller said that "this interpretation committee" would be advisory to the full Board of Governors. Neither the United States nor Saudi Arabia -- the principal protagonists in the scrap over the PLO will be on the new advisory group. The substantive question of how to deal with the overall question of which observers will in the future be admitted to annual meetings is still to be decided by the entire 22-man board of each institution by March 31, 1981, Miller said.

Rashidzadeh, who is also vice governor of the Bank Markazi Iran, labeled the U.S. freeze "a dangerous weapon" which denied Iran use of substantial amounts of an international reserve currency that it owned. "When a single government could stop the free use of a so-called usable currency, this would seriously lessen the credibility of the [IMF] Articles of Agreement," he said.

But Miller responded, as U.S. government officials have reiterated before, that the freeze of assets came 10 days after Iran seized more than 50 American hostages and to forestall other illegal acts on the part of Iran. The United States hasn't taken title to or used the Iranian assets, he said, "And when the hostages are released, the [Iranian] assets will be released."

As to Rashidzadeh's argument that the IMF had failed to take the proper steps to protect Iranian interests, Miller said that IMF regulations fully recognize the right of a country to take the kind of action that the U.S. took, when taken to protect national security.

Rashidzadeh's operative demand seemed only to be an insistence that the Tanzanian chairman of the joint meeting, Amir Jamal, mention "our grievances" in his final report to the session this morning, "so as to show that there is at least a world forum where such legitimate voices of discontent can be attentively heard."

Miller indicated that the U.S. is highly pleased with the overall results of the current joint meeting, which he said demonstrated that both the Bank and the IMF are responding actively to the increased need of the poor countries for loans to cover their international deficits.

As a general evaluation, he predicted that there would be "no problems" this year in recycling (that is, relending) surpluses held by the oil cartel countries and that recycling would not be a serious problem in 1981. But he acknowledged that there was "considerable concern" whether the international monetary system will be in a position to meet the demands in succeeding years. "There is no pessimism, just concern," he reiterated.

He noted with appoval that the less developed countries, which at earlier meetings had complained that the institutions were sticking too close to "the status quo," this time acknowledged that there was movement in the direction they had been urging. He cited, especially, the approving comments that had been made by Indian Minister of Finance Ramaswamy Venkataraman.

For the long run, Miller said that he didn't think the debate over the PLO issue will result in the "willingness of the [oil cartel] countries to participate" in the larger financing that both the IMF and World Bank will require to match the new flexibility in their lending standards.

"There is a cooperative attitude and good-will all around," Miller said. He revealed that, "as one more step in building bridges all around the world," he had invited Saudi Arabian and American business leaders to meet for a two-day session, beginning today at the Treasury, to discuss business investment opportunities in Saudi Arabia.