Ayatollah Ruhollah Khomeini today called for an army of "20 million" Iranians to take on the U.S. enemy, termed "100 times stronger" than the vanquished shah Mohammad Reza Pahlavi and his armed forces.

Despite the martial note Khomeini sounded in receiving a group of Revolutionary Guards in the holy city of Qom, the thrust of his message was to buck up Iranian spirtis in the confrontation with the United States, described as a "force which has no rival."

"Your country is in a situation that if you don't move quickly enough, we'll all be destroyed," the 79-year-old religious leader said."

Analysts noted that Khomeini's militant tone appeared dictated by a desire to create maximum public acceptance for his controversial, hand-tailored constitution, which is to be voted on in a referendum Sunday and Monday.

He was expected to maintain the fever pitch of his anti-U.S. campaign throughout the week, especially Thursday and Fridy, which are the holiest days for Shiite Islam's annual Moharram month of mourning.

Indeed, the religious holidays and the referendum were invoked to explain the embarrassing about-face last night that first had Acting Foreign Minister Bol Hassan Bani-Sadr flying to attend a United Nations Security Council meeting, then abruptly postponing his trip for a week.

The ruling Revoluntionary Council vetoed the trip after Bani was ready to leave for the airport, according to informed sources.

Bickering inside the Revoluntionary Council apparently accounted for the decision, which did little to improve chances of any quick release of the remaining 49 hostages held in the U.S. Embassy since Nov. 4.

Bani-Sadr, who has never hidden his distaste for the hostage operation in his desire to solve the crisis expeditiously, was overruled by Revoluntionary Council members who apparently resented his constant hints of tactical concessions.

Specifically, in a variety of guises, he has suggested formulas that stop short of the hardline demands for the shah's unconditional extradition by the United States to stand trail here. That has been the goal of the radical Islamic students occupying the embassy.

In his address to the Revoluntionary Guards, Khomeini said, "Equip yourself, get military training and train your friends."

"Give military training to those who are not trained," he said. "In an Islamic country, everyone should be a solider and have military training."

He urged that a "country with 20 million young people" should have "20 million riflemen, an army of 20 million."

In a separate developement, an unidentified group attacked an Air Force base in western Iran, causing serious damage to it and a televison transmitter there, according to a Radio Tehran broadcast monitored in London.

The broadcast said security forces rushed to the site near the Iarqi border, and that three base guards had been wounded in the machine-gun and grenade attack.

In Tehrna, three young American women who described themselves as representing a newly organized committee of "about a dozen" U.S. women married to Iranians and living in Iran publicly endorsed the occupation of the U.S. Embassy today and said the 49 hostages should be tried as spies.

For the second straight day, meanwhile, Marxist-Leninst Fedaye Khalg guerrillas and their sympathizers marched toward the U.S. Embassy, but were turned back by Islamic militants before they arrived.

The newspaper Islamic Republic, close to Khomeini's clerical thinking, charged that some 10,000 Fedaye Khalg who took part in yesterday's march acted "to save themselves from political bankruptcy." That was an allusion to the radical left's decision during the summer to go underground rather than confront Khomeini's numerically superior Islamic forces.