Newly appointed Iranian Prime Minister Mohammed Ali Rajai called on revolutionary leader Ayatollah Ruhollah Khomeini today before launching the difficult task of choosing a Cabinet.

Rajai, a former schoolteacher and education minister favored by hardline Islamic clerics, said his government would give unbending loyalty to Khomeini.

Iran's parliament, which overwhelmingly endorsed Rajai yesterday, has been charged by Khomeini to solve the long-running American hostage crisis. Its work had to be postponed, however, until a prime minister and Cabinet could be named.

The 52 remaining hostages are in their 283rd day of captivity.

Rajai told reporters after parliament approved him that according to the constitution he has 10 days to form and introduce his Cabinet and that this period would be sufficient.

The parliament, which meets again Saturday, must approve the Cabinet just as it did Rajai, and little opposition is expected.

"In forming the Cabinet, I would seek assistance and cooperation from all revolutionary foundations and rely on these institutions," the official Pars News Agency quoted Rajai as saying.

he said so far he has not chosen any Cabinet member, but that the criteria for such selection would be those stressed by Khomeini, Iran's Shite Moslem patriarch.

"The only condition I add is that a person who is appointed should accept the religious leadership of the imam [Khomeini]," Rajai said.

He said President Abol Hassan Bani-Sadr -- pressured into nominating Rajai by the Moslem fundamentalists who dominate parliament -- "has no opinion on the selection of the Cabinet ministers and has given me freedom of action in this respect." But Rajai insisted, "I being to the masses and am brother with the president and together we will serve the nation."

Bani-Sadr visited Khomeini today at the end of Ramadan, the Moslem holy month, and spoke for 50 minutes "about the latest development of the country and current problems," Pars said. Bani-Sadr was quoted as saying Khomeini "gave directions for creating an atmosphere of understanding."

The religious leader has so far refused to involve himself directly in the formation of a government, although ministers and politicians visit him often.

Apart from chiding the president and parliament for clashing frequently, his speeches in recent weeks have concentrated mainly on asking Moslems around the world to learn from Iran's Islamic revolution.

He again commended various aspects of the revolution today to 30 ambassadors, mostly representing Moslem states, who called at his house in suburban Tehran.

Meanwhile, Tehran radio reported today that 155 insurgents were killed Sunday in a clash with Iranian government forces staging a "mopping-up operation" in strife -torn Kurdistan around Baneh, near the Iraqi border. There was no mention of government casualties. The area has been the scene of fierce fighting between Iranian government forces and rebels seeking independence for the Kurdish region.