ALL THROUGH Friday night into Saturday morningit seemed there would be an early "happy end" to the hijack crisis. This was the forecast of Syria, which had moved in boldly to untie the diplomatic knot by arranging to receive the hostages from their Lebanese captors. The transfer would have meant that the United States and Israel were no longer dealing in their respective ways with terrorists but, again in their respective ways, with an established state. On this basis the Americans and Israelis could at once preserve their refusal on principle to make concessions at gunpoint and find a formula for the natural swap -- an exchange of the Shiites' American hostages for Israel's Lebanese ones. To make the Syrian option work has to remain the pressing policy goal.

What derailed it at least temporarily was the Shiites' public demand that the United States pledge not to retaliate. Would the Shiites have voiced this demand if President Reagan, during a phase of sensitive diplomatic exchanges the day before, had not branded the hijackers "thugs, murders and barbarians" and warned that they would be "held to account"? Did the Shiites cleverly wait for the Syrians and Americans to start tasting the success of their diplomacy, in the expectation that that would be the best moment to secure a no-retaliation pledge -- and to consummate a Shiite political coup?

We're not sure, but at this point it should be clear that it does no good for the administration or anyone else to flog the possibility of retaliation. Everyone can see the pressures on Mr. Reagan to deliver a bashing. You don't have to be much of a mindreader to imagine what the president's instincts are. Certainly we find it infuriating to have to hold off delivering the message that Americans cannot be terrorized -- one TWA passenger, rememity.

Even before Mr. Reagan and the Shiites conducted their public exchange, however, Washington had to consider how retaliation, after the release of the TWA 39, would affect the fate of the earlier American seven remaining in radical Shiite hands. And if those seven are released now or later, Mr. Reagan must then satisfy himself that retaliation would not provoke the capture and complicate the plight of another group of hostages.

From his left the president is belittled for having criticized his predecessor for hedging the way he is hedging now. From his right he is being attacked for lacking political virility. Neither taunt helps a responsible president address the difficult choices -- choices involving human lives -- that lie before him.

The hijacking was criminal. All the hostages -- and the earlier seven -- must be kept from further harm and freed at once. In getting them back the United States must not jeopardize other Americans. These are the rock American considerations.