Ronald Reagan is not the first president to assert the United States' vital interest in the security and stability of the Persian Gulf. But if he is not careful, he could become the first president to involve the United States in war in this violent region.

Almost all of America's friends in the Mideast, Europe and South Asia are worried that a major commitment of American forces would be dangerous to U.S. power as well as American lives.

No one doubts that the Iran-Iraq conflict is a terrible war with a worrisome potential for destabilizing the area. No one believes there is an end in sight to this conflict that has already lasted seven years. Efforts to negotiate peace, secure a cease-fire or cut off weapons supplies have all failed.

In the last few days, a new U.S. effort to persuade the five permanent members of the U.N. Security Council to impose a real, global arms embargo failed. The proposal was not even supported by our good friends and allies, France and Britain, who both have a naval presence in the Gulf. Despite Europe's pressing need for Gulf oil, these allies have resisted American proposals for a larger joint effort to protect Gulf shipping.

The Reagan administration, already burned by an unsuccessful effort at peacekeeping in Lebanon, should reflect on the allies' reluctance. Their experience with the complicated violent politics of the area is greater than ours, as is their vulnerability to interruption of Gulf oil.

From our point of view -- as I understand it -- the U.S. government is appalled by the terrible carnage of this bitter war, worries that it will expand and engulf the region, and is concerned at the increasing Soviet role. Our sense that the situation is deteriorating, our regrets at having assisted Iran (however marginally), our desire to do something dispose us to action.

Our allies have different predispositions. They, too, understand the war is terrible, but they note that in seven years it has been contained. They see the more active role of other countries -- especially the ''super powers'' -- as itself constituting a dangerous expansion of the conflict. Therefore, they prefer to see a continuation of the low-profile U.S. role and a quiet response to the Soviet offer to ''protect'' two Kuwaiti tankers.

They see the Soviet offer to Kuwait as another manifestation of Mikhail Gorbachev's new diplomacy in the Middle East, which has already led to restoration of diplomatic relations with Egypt, Oman and the United Arab Emirates, and Soviet participation in negotiations concerning a resumed Arab-Israel ''peace process.''

While these Soviet initiatives are not welcome to our allies, the allies have no fondness for collective action, and regard it as safer for Gulf countries to continue to muddle through than to risk an East-West conflict.

Defense Secretary Caspar Weinberger's ''tests'' of when and where to commit U.S. forces could be useful in hammering out a new U.S. policy.

Is the area vital to American national interest or those of our allies? The energy-rich, strategically located Persian Gulf has been regarded by recent American presidents as an area of vital interest. Today, however, only 7 percent of American oil comes from the area. Our allies and friends are much more dependent than we on Gulf oil, but do not feel an increased military presence is necessary or desirable to protect their vital interests.

Do we have clearly defined political and military objectives? Securing free passage of ships in the Gulf is a clear limited objective. Is that the sole U.S. concern? Keeping Soviet influence out of the region is a far more difficult, ambiguous objective because the Soviet Union already has major influence in the politics of North Yemen, Syria and Kuwait. The large goal of ending the Iran-Iraq war and bringing peace to the region would be truly difficult to accomplish.

Do we have a clear commitment to win? It depends on the objective and the costs. There are surely costs Americans would be unwilling to pay to ''pacify'' the Iran-Iraq conflict.

Can we count on the support of the American people and the Congress to achieve the objective? Again, it depends on the cost. Polls show strong public support for a continued U.S. presence to provide free passage. But the complicated, morally ambiguous politics of the Middle East are not attractive to most Americans, nor are they likely to become so. They do not fit our national need for a foreign policy based on clear moral objectives. Moreover, the current Congress can hardly be counted on to maintain a coherent or responsible position on any issue except its own power.

Is the U.S. commitment of greater force a last resort? Most countries in the region -- including Egypt and Saudi Arabia -- believe there are other options still to be explored.

There are no unambiguous answers to these questions. That fact alone should give the president and his advisers caution about deeper involvement in this area, where carefully negotiated agreements unravel even as they are signed and almost everyone wants something more than he wants peace.