Washington — Taking into account economic, strategic, and domestic political factors, President Reagan has adopted a low-key, restrained policy in the Gulf region. Through a modest amount of aid to Saudi Arabia and diplomatic moves, President Reagan is carefully avoiding direct United States involvement in the region and trying to contain the widening Iran-Iraq war.
Diplomatic and academic experts give the President credit for keeping the focus on Persian Gulf allies and doing what he can to give them confidence in their own ability to deal with the problem. Some administration officials suggest that Mr. Reagan has in fact pulled back from his earlier pronouncements about keeping open the Strait of Hormuz at all costs.
''There has been a redefinition of that,'' one officialcomments. ''He is stressing that the US would help only if there is a clear, publicly stated requirement for that, not just a private one.''
''We're still concerned about freedom of navigation,'' says another administration official. ''If the shipments of oil stopped, that would concern. But at this point the Gulf is still open to shipping and the oil is moving. The situation is serious but does not appear to be critical.''
Two developments this week are designed to bolster the self-confidence of Saudi Arabia and the other Gulf states:
* The administration announced Tuesday that it had sold and transferred 400 shoulder-fired Stinger antiaircraft missiles and 200 launchers to Saudi Arabia. It is also providing one US Air Force KC-10 aerial tanker, to be manned by US crews, for refueling Saudi Arabia's F-15 fighters.
The purpose of these supplies is to help the Saudis protect oil installations and shipping in the Gulf. An American team will be sent to help train Saudi forces in use of the Stingers.
* The United States is scheduled to speak in the United Nations Security Council on behalf of a peaceful resolution of the Iran-Iraq conflict. Administration officials say the US will deplore escalation of the attacks against oil tankers and, although especially critical of Iranian actions, will not deliver a strong rebuke, in an apparent effort to keep from inflaming the situation.
Further diplomatic moves, say State Department officials, include intensive diplomatic consultations with Washington's allies on finding some means of reducing the supply of arms to Iran from various quarters, including the Soviet Union.
Because of the President's careful policy of keeping the Gulf states, and not the US, out front, Congress is not expected to oppose emergency sale of the 400 Stingers to the Saudis. Under the US Arms Export Act, the President can make such a sale without the required 30-day review by the lawmakers. Further sales - the original proposal called for sale of 1,200 missiles and 400 launchers - would necessitate congressional consu,tation.
''I doubt there will be much resistance to the sale of 400 Stingers or the tanker plane,'' a House congressional source says.
''If the refueling tanker is only on loan, I doubt (there will be) much fuss, '' comments a Senate Foreign Relations Committee aide. ''As long as we're letting someone else protect the area, not much pressure will build up here.''
The sale of the heat-seeking Stinger missiles is seen as having a psychological purpose. ''It will take weeks before anyone shoots them,'' comments Philip H. Stoddard of the Middle East Institute. ''The Saudis have never fired in anger and have virtually no combat experience. But having this equipment and the people giving them training gives them psychological reassurance.''
After the disastrous experience in Lebanon, diplomatic and other experts say, the Reagan administration appears to be leaning more heavily on experienced Mideast hands in the State Department.
There is still no overall policy for dealing with the multiple problems in the Middle East, including the Arab-Israeli dispute. But the present general approach to the Iran-Iraq war and defense of the Gulf is in line with approaches pursued over several administrations; that is, trying to give the Gulf states a capability of protecting themselves and Gulf shipping.
While analysts believe Mr. Reagan is handling the present crisis with due restraint, some say that more-concerted efforts should be made to persuade Iraq to call off the tanker war.
William Quandt of the Brookings Institution suggests the administration might give Iraq another alternative to war by helping it get moving on its oil pipeline project - building a line from southern Iraq to Jordan. This, he says, would secure the export of its oil, put more oil on the world market, and give Iraq a stake in stability in the region.
Administration officials say the US does favor the idea of the pipeline, which would be built by Bechtel Corporation and has been under discussion for several years. This would require US financing, however, and that is but one of the problems that needs to be addressed. Another is convincing Israel, which is hostile to Iraq, that such a project would be in the long-range interest of regional stability.
''We are interested in the project,'' says a high State Department official. ''We don't want to see the Khomeini brand of fundamentalism sweep through the Gulf, and the first barrier is Iraq - even if Iraq is not all that attractive.''
As for the current tanker war, the official says the administration is seeking to do ''what makes sense.'' That is, to ''let the states in the region manage the problem, which is what they want to do.''