A SECOND diplomatic initiative has now come from Saddam Hussein, and it's a good deal more interesting than his first, which was merely to say that once the Mideast's other disputes are resolved, Iraq may consider evacuating Kuwait. Iraq, you will recall, went to war with a supposedly revolution-enfeebled Iran in 198O primarily to take control of both banks of the Shatt al Arab waterway lying between them. Now President Hussein offers to accept the old midstream border and meanwhile to start releasing the Iranian lands and prisoners he has been holding for negotiating leverage since the 1988 cease-fire. It's not quite clear what he expects in return, but that seems to be the gist of his message to Tehran.

A cynic might say that with Kuwait now annexed, Iraq doesn't need the Shatt -- that abandoning a historic claim to a waterway clogged for 10 years is a mild price to pay for retaining a valuable new conquest and for bargaining Iran out of the anti-Iraq coalition. But this overlooks the political risks Saddam Hussein takes by suddenly abandoning, in only the second week of his Kuwaiti campaign, the supposedly sacred national cause for which he led Iraq to battle with immense losses in blood and treasure. It is hard to believe that even the most ruthless dictator can confidently seal himself off from the consequences of surrender of the goals and fruits of a decade's war.

In the United States, discussion is deepening on the issues of purpose and policy raised by the American response to Iraq's grab of Kuwait and its threat to Saudi Arabia. Though American opinion, like much of world opinion, appears generally supportive, the ''what ifs?'' are under intense and nervous canvass. This is the American style, and it can serve American policy well. The discussion needs to keep in mind, however, that international and regional resistance to his aggression is giving Saddam Hussein some cares of his own. Is it accidental that he makes a lavish bid for Iran's favor just as his single sympathetic (and dependent) neighbor, Jordan, comes under a range of countering pressures and inducements from the United States and others?

This is a time for steadiness, not for premature relief. But if Iraq is a long and dangerous way from retreat, it is also a long way from victory.