Washington's latest warnings to Iran through the press reflect growing concern that some brainwashed American hostages, after a month and a half of captivity, may be trotted out to tell an Iranian-sponsored "international tribunal" about the past "sins" of the United States.

Political, as well as humanitarian, considerations make such a possibility abhorrent to policymaking circles here. The impact at home of such testimony in a show trial or tribunal could by explosive -- and it would make the drawn-out, unpredictable and complex Iranian crisis even more difficult to manage at the U.S. end.

In the continuing absence of direct diplomatic contact, communication through the news media is the quickest -- if not always the most reliable -- channel for the exchange of messages. The past several days have seen new demonstrations of the usefulness and the pitfalls of diplomacy by journalism.

The words from Iran, as usual, have come in torrents from competing centers of power: moral and poltical absolutism from Ayatohhal Ruhollah Khomeini: sleight-of-hand suggestions for reassurances and accommodation from Foreign Minister Sadegh Ghotbzadeh: unyielding invective from the "student" captors, reflecting self-confidence and a sense of self-importance.

From the U.S. perception, this fragmentation of authority in Iran is bedeviling and overpowering. The words of student militants now openly attack the words of the foreign minister, as occurred Tuesday in No. 75 of the series of daily student communiques, issued Tuesday.

At the same time, Khomeini says it is "a calumny" that the students are directing Iranian foreign policy, even while he is defending the positions they take.

In his most recent press interview on Sunday, Khomeini complained that Americans are so poorly informed that "it is all too possible that they have not even heard the name of Iran." He added that "the pen in the hands of the foreign press is a pen in the hands of the enemy, something that is worse than the bayonet to the fate of mankind."

The State Department took pains yesterday to knock down the latest journalistically conveyed missive from Tehran: Ghotbzadeh's suggestion in a Washington Post interview that an official U.S. investigation of the deposed shah's alleged crimes could end the crisis.

Spokesman Hodding Carter said such a U.S. gesture before release of the hostages would be surrender to blackmail -- even while officials acknowledged that the United States is seeking to explore what Ghotbzadeh had in mind and what, if anything, it means.

The latest Washington initiative in the public exchange was a White House statement Tuesday that "public exploitation" of the hostages through appearances at an International tribunal could be "a further provocation," bringing grave consequences. The warning was reinforced by official hints, conveyed to reporters as a not-for-attibution guidance, that certain types of U.S. military action could be triggered by such a provocation.

The suggestions about military options, even though clearly deliberate and intended to be widely conveyed, were anything but specific. Reporters were told there is a wide range of options more punitive than anything done so far, but which still need not involve shedding blood.

Reporters asked persistently about a naval blockade of the Persian Gulf, which seemed to be one such non-bloody military action in the realm of possibility. They were given no official encouragement and at one point were steered away from that option. Nevertheless, the idea of a blockade gained prominence in some accounts.

Tuesday's warning was the second such hint of possible military action from the White House during this crisis. The earlier suggestion, in a statement and background guidance on Nov. 20, came in response of the threat of quick spy trials. The trials did not develop, and some U.S. officials believe the threats of military action had an effect.

It seems less likely that the U.S. warnings will head off the "international tribunal" on the "sins" of the shah and U.S. policy that Ghotbzadeh has been promoting assiduously since becoming foreign minister three weeks ago. He is armed with a signed "instruction" by Khomeini dated Dec. 13 and broadcast on Tehran Radio, to convene such an international investigating committee as soon as possible. Some international political figures reportedly have been approached to participate. But the role of U.S. hostages in such a show -- and the impact on their future -- is much less clear.

At this point in the long-running crisis the war of words fills the newspapers and the newscasts, but it is misleading about the underlying reality. In fact, this is less a period of motion than a period of expectant waiting for more serious movement.

The stage has been set: In Iran, the Islamic holy days are over and the new constitution has been adopted. In the world community, the U.N. Security Council resolution has been unanimously adopted, and the International Court of Justice opinion unanimously handed down. The deposed shah has left the United States.

In the U.S. official view, the outside pressures on Iran -- both diplomatic and economic -- slowly are gathering force. Spade work is being done toward generating further pressures, probably through a U.N. Security Council resolution calling for economic sanctions.

What is still missing is a clear sign that any of this is having an effect on releasing the hostages in the U.S. Embassy. Because of the complex power relationships in Iran, the main chance for the United States under the current arrangement is to hope for a three-bank shot, affecting the outside environment and the connections of the foreign minister and those members of the Revolutionary Council attuned to external reality, in the hope that they will affect the actions of the ayatollah in Qom, in the hope that he can issue orders to the student militants in the embassy.

It is a Rube Goldberg arrangement for dealing with an international problem worse than the nightmare scenario of the most improbable books of Washington fiction. Unhappily, the Iran crisis is fact rather than fiction and Washington has yet to fathom the basic plot.