The situation in the Persian Gulf is very dicey. Iran is crushing the Iraqi forces that invaded 20 months ago and, while threatening to continue a military and subversive offensive, demanding both the ouster of strongman Saddam Hussein and the payment of $50 billion in reparations. "We have very unhappy memories of the Arab-Israeli truce," an Iranian official told The Wall Street Journal. "Once you accept a truce, you never get anywhere with negotiations."

But this is only the half of it. The Iranians are now looking afield to the conservative Gulf Arabs who have been backing Iraq--with an estimated $22 billion last year. The revolutionary Islamic regime in Tehran is anticipating in particular "a much humbler Saudi Arabia. Their pretensions to power and influence in the Persian Gulf will fade very quickly," the oil minister says. For the Gulf states, the danger is not so much an outright invasion as the internal unrest that could be produced by Iranian manipulation of local Shiite Moslems.

This emerging change of Iranian focus from Iraq to Saudi Arabia is a matter of no small consequence to the United States. In the Iraq-Iran war, the United States could strike an essentially neutral position; Secretary of State Haig underlined it the other evening. That war pitted an invading Arab state with which Washington has poor relations against an Iranian regime with which Washington had just gone through a nightmare crisis.

In any confrontation between Saudi Arabia and Iran, however, the United States could not easily stay detached. There is Saudi oil. The Saudis are an American favorite--hence Ayatollah Khomeini's warning to Saudi Arabia to "give up taking orders from the United States and treat us in accordance with Islamic laws." The Reagan administration, moreover, has made an explicit commitment to protect the House of Saud against internal as well as external foes.

A worried United States now promises to "take a more active role," with others, to find a settlement preserving the sovereignty and territorial integrity of both Iran and Iraq. Secretary Haig warns, "We have friends and interests that are endangered by the continuation of hostilities." But the primary responsibility for maintaining stability in the Gulf falls on the countries there. The Iraqis must decide in their fashion whether Saddam Hussein's leadership still serves their interest. They seem prepared to consider reparations, if a face-saving way of assessing payment can be found. The Saudis are debating, The Journal reports, whether to give Iraq the money. It is not a pretty picture. But it is better than a spreading war, or a spreading revolution.