AYATOLLAH KHOMEINI spoke a message of defiance to Americans on television yesterday. But, nonetheless, a certain impression is being conveyed from Tehran of a revolution becoming aware by stages that it is riding a tiger. It was easy enough to seize the U.S. Embassy 15 days ago and demand that the cancer-stricken shah be removed from his hospital bed in New York to Iran. But the steadfast refusal of the Carter administration to make that deal and the near-unanimous support of the administration by the American people and the international community have put the Iranians in a bind. How can they cut short the losses they have incurred by grabbing the American diplomates without losing face? How can they get off the tiger?

A partial answer is suggested by their announced decision to free at least some women and non-whites among the Americans held at the embassy. This is said to reflect the special respect in which Islam holds women, and the oppressed condition of blacks. That's just fine. Some of the most telling reproaches leveled against the ayatollah in this crisis have come from Moslems and non-whites. It is good that he feels it necessary to make gestures to them.It is quite another matter, however, if he or other Iranians think that by releasing black and women they can peel those elements off the body of American opinion backing President Carter's demand for an immediate release of all the hostages. We hope Iran's diplomats in Washington can help set their countrymen straight on that score.

The ayatollah insists that the remaining hostages will be screened and that those found to be spies will be tried and punished under Islamic law. There is a welcome hint here that hostages found not to be spies may be eligible to have their diplomatic immunity restored, and perhaps to be released. That would be one additional way to get off the tiger. But that would still leave the "spies," who, the ayatollah claims, "are no longer diplomats" and therefore are not protected by immunity. It is important to note here that this is a totally specious distinction. Under the law and practice respected everywhere else, all people with diplomatic status enjoy immunity, regardless of their embassy function. That he reaches to the realm of "Islamic law" to justify this outrageous prospect suggests he realizes how weak his position is. If the ayatollah goes ahead with trials, he will make Iran even more an international pariah than it already is.

The suggestioln is heard from Iran that the revolution may stage such trials to make a symbolic demonstration of the reversal of Iran's earlier status as a dependency of foreign powers. But Americans cannot conceivably accept any effort to satisfy the "inner needs" of the Iranian revolution at the expense of the hostages. The United States has offered the ayatollah a full international hearing, at the United Nations, for any arguments he may wish to present -- as soon as all the hostages are freed. Until then, he is completely responsible for their well-being.