More than 400 placard-waving Iranians opposed to the Ayatollah Ruhollah Khomeini demonstrated yesterday in front of the White House, trading shouts with a small but vocal band of Khomeini supporters before dispersing peacefully.

A combined force of about 150 U.S. Park Police and D.C. police, including more than a dozen on horseback and 50 on motorcycles, kept the two groups far apart, insuring that the violence that has marked past Iranian demonstrations was not repeated.

Sponsored by the Iranian Freedom Foundation (IFF), the rally, punctuated by chants of "Death to Khomeini" and "Long live the Shah", featured a series of speakers who called for the overthrow of the Islamic Republic of Iran and the restoration of the Pahlavi dynasty.

IFF director Mohammed Tabatabai, twin brother of slain IFF founder Ali Akbar Tabatabai, who was assassinated a year ago at his Bethesda home, emphasized yesterday that the IFF opposes not only Khomeini but the leftist Peoples' Mujaheddin Organization of Iran, which briefly took over and ransacked the Iranian Interest Section of the Algerian Embassy here on Friday.

One demonstrator was shot, two other persons injured and 24 demonstrators jailed in that incident, the latest in a bitter and intensifying factional war among expatriate Iranians.

The IFF, which draws support mainly from the middle-class, professional and former military sectors, claims support among several conservative groups within Iran and in exile in France, especially elements of the armed forces, Tabatabai said in an interview before the rally. He predicted his supporters would be demonstrating in the streets of Tehran within six months.

Another supporter, who asked not to be identified, said the group favors army intervention to get rid of Khomeini and restore a constitutional monarchy, conceding that that would be the only way for the IFF to succeed.

The well-dressed crowd sat in the wet grass and cheered as Tabatabai, the featured speaker, denounced Khomeini and his supporters as "rabble-rousing agents of evil," who exploited the religious feelings of "simple folk."