Exiled Iranian former prime minister Ali Amini, 75, called on the Iranian opposition yesterday to unite under his umbrella in preparation for what he said would be the fall of the government of Ayatollah Ruhollah Khomeimi.

He is understood to have the private backing of the most important ex-military leaders in exile, according to Washington Post correspondent Ronald Koyen.

Amini in effect offered himself as an alternative to Shahpour Bakhtiar, the shah's last prime minister, as an overall leader for the opposition. Bakhtiar's continued close relations with the Iraqi government close relations with the Iraqi government, even after the Iraqi invasion of Iran is "indefensible," said Amini, who served as ambassador to Washington in the late 1950s, reported that American Cynthia B. Dwyer denied spy charges in court Wednesday and the prosecutor said she was drawn into a fictitious plot to free the 52 American hostages.

A report in the Perian-language paper said the prosecutor indicated that the 49-year-old mother of three had been tricked by two Revolutionary guards who made up a story about an armed band of students who wanted to free American hostages.

According to the newspaper's fragmentary report, the posecutor said Dwyer agreed to help and tried to obtain guns and radios equipment to aid the plan to free the hostages. She was arrested May 5 after going to Tehran for what she described as an effort to write about Iran.

Ettelat, the only Iranian newspaper to provide an account of the trial, did not offer details of the session but carried purported quotations from Dwyer saying she had tried to transmit a message to one hostage. It quoted her as denying she was a spy and saying she was in sympathy with the Iranian revolution.

In another development, 23 Iranian deputies formally requested a parliamentary debate on the American hostages, as a political row over their detention and the terms of their release gathered momentum.The group made its request in a letter to the speaker, Hojatoleslam Ali Akbar Hashemi Rafsanjani.