Ayatollah Ruhollah Khomeini announced today that a constitution for his planned Islamic republic has already been drafted and would be submitted to Iranians for approval in a referendum.

The surprise announcement apparently means that Khomeini changed his mind some time ago about plans for a democratically drafted constitution for his proposed government.

Khomeini, the Moslem leader who returned here Thursday after 14 years in exile, hopes to supplant Prime Minister Shahpour Bakhtiar and the monarchy of Shah Mohammad Reza Pahlavi, who is on indefinite vacation out side Iran.

Khomeini's chief political strategist in Iran and his top adviser at his exile headquarters in France both had said previously that a constituent assembly would be convened as an integral part of forming the Islamic republic with which the Shiite Mosiem leader intends to replace the current government.

The constitution that has been drafted "will be put up for public vote so that an Islamic republic will be established," Khomeini said at his makeshift revolutionary headquarters here. Nothing in his statement nor his answers to reporters' questions suggested that the constitution would evolve from elected representatives of the Iranian prople.

Khomeini also said he will announce the creation of a provisional government "very soon," and that the members of a revolutionary council -- which will first appoint the provisional government and then prepare for the constitutional referendum -- have already been selected. He did not name the members.

Medhi Bazargan, who has emerged as Khomeini's chief political adviser here, and Sadegh Ghotbzadeh, who served as a top aide at the opposition leader's suburban Paris headquarters, repeatedly had said a constituent assembly would be part of the writing of a final constitution draft to be put to the voters.

Bazargan and Ghotbzadeh represent, respectively, moderate and hard line segments of the occasionally divided Khomeini camp.

Western diplomatic analysts took special note that Khomeini again postponed the announcement of a revolutionary council, which had been expected Thursday and again today.

It is believed that Khomeini is counting heavily on an agreement with the Iranian army, while he continues to wage a war of political attrition with Bakhtiar for defections from the government.

About 70 of the 282 members of the parliament's lower house have already resigned, and Khomeini's supporters say that it enough members quit, Bakhtiar's government will no longer have a legal basis to stay in power.

As if to reinforce that strategy, Tehran Mayou Javad Shahrestani approached Khomeini at today's news conference, kissed his hand and said he was resigning from the "illegal" government.

Khomeini said there have been "contacts to invite the army to rally to the people... there have been some contacts to guide tham for their own good."

Bakhtiar continued to insist that the army is solidly behind his government, and that he would ignore any provisional government named by Khomeini.

In a French radio interview, Bakhtiar said Khomeini's followers "can insult, clamor and howl -- it signifies nothing."

Khomeini, asked at his press conference whether he would call for a jihad (holy war) if Bakhtiar refused to capitulate, replied, "If our mode of struggle does not work then we will be obliged to ask the people to take up arms."

The 78-year-old Moslem leader has said repeatedly that an armed struggle may be necessary.

Outside the auditorium of Khomeini's headquarters, a former girls' school near the parliament, about 1,000 supporters chanted, "Long Live Khomeini," and thousands more waited outside the gates to the school for a glimpse of him.

Tehran was quiet throughout the day, with some signs of normality returning. Although a general strike has shut down most of the city, a few shops have begun to open, and some street venders are appearing once again.

The lack of an effective air control system at Tehran's international airport, however, forced several international airlines to cancel flights, stranding hundreds of passengers.

Meanshile, Iranian Foreign Ministry officials allied with the opposition charged that the Bakhtiar government had secretly informed the U.S. State Department that Ardeshir Zahedi has not been dismissed and should be still considered Irans's ambassador to Washington.

Mohammed Alikhani, a former counselor and head of the financial section of the Iranian Embassy in Washington, said that although the Bakhtiar government claimed to have dismissed Zahedi, it recently sent a cable to the Iranian Embassy ordering that a note be delivered to the State Department informing the United States that Zahedi will still be ambassador.