Ayatollah Ruhollah Khomeini, the Moslem holy man who inspired the overthrow of the shah of Iran, today blamed the country's deepening political crisis on "American agents."

Appearing increasingly on the defensive as a key Iranian political leader and another influential holy man intensified their criticism of his rule, Khomeini said, "Mysterious hands are creating disunity in the nation. Satanic plans are under way by America and its agents."

He called for a display of military backing for his Islamic republic Wednesday, which he declared Army Day, and ordered all branches of the armed forces to "parade and show their support."

His call for support came as Karim Sanjabi, who resigned Monday as foreign minister, and Ayatollah Mahmoud Taleghani, a religious leader like Khomeini with considerable following of his own, added new criticisms of Khomeini's revolutionary committees that run Iran as a shadow government.

Sanjabi, at a press conference today, warned that Iran faces "a new form of suppression" and apotential "catastrophe" unless the power of revolutionary committees loyal to Khomeiniis curbed.

He stressed that his resignation Monday was not intended to undermine the government of Prime Minister Mehdi Bazargan but as a "warning signal regarding probable dangers."

"This resignation is a reaction against the emergence and growth of numerous and irresponsible power centers," he added.

Continuing one of the most direct attacks by an influential Iranian political leader on Khomeini's Islamic militias and revolutionary committees, who have been acting independent of the government in carrying out arbitrary arrests and searches and in countermanding government directives in domestic and foreign areas, Sanjabi said:

"Another kind of government has appeared in the shape of numerous forces all over the country which, with their acts, are heralding a new form of suppression. These numerous forces in the form of different armed groups and irresponsible committees . . . show their dominance over the government."

Sanjabi's statement coincided with a similar warning against a return to "dictatorship and despotism" attributed to Taleghani, who left Tehran for a provincial hideout Friday to protest the arrest of his two sons and a daughter-in-law by Khomeini's militia.

The disappearance of Taleghani, who suffered torture under the shah and who is widely respected by all segments of society including liftists, sparked a third straight day of demonstrations in downtown Tehran. Protest marches in which tens of thousand stook part were also reported in several provincial cities.

Sanjabi's statement appeared to signal an attempt by him to breathe new life into the National Front, the coalition of liberal parties that he heads. Its position in the forefront of the political opposition to the shah has declined since Khomeini returned to Iran.

Sanjabi apparently also wants to start building a power base for a possible candidacy in Iran's upcoming presidential election.

By declaring Wednesday as Army Day, Khomeini apparently is trying to counter the demonstrations and statements against his revolutionary committees by putting vast throngs of his followers in the streets as he did during the revolt against the shah.

But it also seems intended to speed up the reconstruction of the Army, which has been paralyzed by the efforts of soldiers' committees to wrest control of the armed forces from the traditional high command.

In what is being interpreted here as a reaction to the appearance of growing turmoil in postrevolutionary Iran, a government spokesman today announced that elections for a constituent assembly and the publication of a new constitution have been postponed indefinitely.

The spokesman, Abbas Amir Entezam, said the constitution is being "revised" by its authors and might be published in another two months.

Meanwhile,a well-placed government source said Sanjabi resigned mainly because of interference in the conduct of the Foreign Ministry and other government departments by Dr. Ibrahim Yazdi, the deputy prime minister for revolutionary affairs and a close aide to Khomeini.

Yadzi's son-in-law, Shahriar Rouhani, has angered government officials here by taking over as de facto ambassador to the United States.

The source said Rouhani claimed to have sent back to Iran embassy documents allegedly revealing Iranian bribes to U.S. congressmen andjournalists but that the Foreign Ministry was completely left out of the matter and does not know where the documents, if they exists, ended up.

[Meanwhile, two of Khomeini's revolutionary committees executed seven more persons early Wednesday for killing innocent persons,Radio Tehran announced.] CAPTION: Picture, Iranian women march in Tehran to protest arrest of Ayatolllah Taleghani's family by the revolutionary committees of Ayatollah Khomeini. AP.