Washington — Given Syria's success in Lebanon and Iran's new offensive against Iraq, the Reagan administration is searching more intensively for ways to create a counterweight to the Syrian-Iran alliance.
The White House on Tuesday reaffirmed President Reagan's commitment to keep open the Strait of Hormuz. It is through this strait that supertankers carry much of the oil that is consumed by Japan and Western Europe.
Presidential spokesman Larry Speakes said that Reagan's commitment included ''doing what's necessary.'' But Speakes declined to comment on reports, carried first by the British Broadcasting Corporation, that a US naval force was moving toward the Gulf. The BBC also said that British ships were conducting exercises to counter any possible action by Iran to close the Gulf.
For the Iranians to attempt to block the Gulf would appear to have devastating consequences nationally, since most of their own oil travels through the Strait of Hormuz. There seems to be considerable confidence here that even if the Iranians did attempt such an action - through mining or the sinking of a supertanker - the United States and its European allies would be capable of reopening the strait.
What has analysts here most worried for the moment is the possibility of an Iranian breakthrough on the battlefield against Iraq. The big question mark for US-supported nations on the southern side of the Gulf is the condition of the Iranian Air Force. It has been assumed that because Iran has made no major aerial bombing attacks on Iraq for over a year, the Iranian Air Force is in a state of disrepair. But some analysts wonder if the Iranians have been husbanding the remnants of their Air Force, readying it for action should the fighting spread beyond Iraq.
Some months ago, the US began reexamining its neutrality vis-a-vis Iran and Iraq. The decision was made to maintain a hands-off military posture in the conflict but to help bolster the hard-pressed Iraqi economy and to give Iraq political and moral support. Ambassador Donald Rumsfeld, President Reagan's special envoy, visited Iraq in December. By helping Iraq, the administration has hoped to restrain Iraqi impulses to escalate the conflict.
Christine Helms, an analyst at the Brookings Institution, has pointed out that the US might need a strengthened relationship with Iraq for leverage against Syria.
''If Iraq collapses,'' said Dr. Helms, a research associate who has visited Iraq several times in recent years, ''then Syria will become a new regional superpower. Iran's capacity to export its brand of extreme Islamic conservatism will be greatly enhanced.''
''What is often overlooked is that the greatest battles going on in the Middle East are over political ideology,'' said Helms. ''The greatest fear of the moderate Arab leaders is not that Iran will attack the oil fields with airplanes but that the Ayatollah Khomeini will undermine their political legitimacy.''
The fear that Iran might try to block the Strait of Hormuz first came to public attention in the middle of last year after Iraq threatened to attack Iranian oil production facilities.
The threat seemed to have some teeth in it because of Iraq's acquisition of French Super Etendard jet fighters carrying Exocet missiles.
Iran responded that it would retaliate by blocking all oil shipments through the Strait of Hormuz. The threat lacked logic, because Iraq's meager oil exports do not go through the strait. Most of Iraq's oil is exported through Turkey.
After initially opposing the French sale of jets and missiles, the Reagan administration appeared to acquiesce in the deal. There are clearly divisions within the administration over how far the US should go in attempting to assist Iraq. But the administration has taken some modest steps in that direction. It has looked for means of assisting Iraq to export more of its oil, tried to discourage Americans and others from selling arms to Iran, and tried to encourage American businessmen to look also at Iraq as a nation with great resources and a good credit rating. The US has also placed Iran on its ''terrorist list.'' And it has stated that it would intervene to guarantee neutral nations the right to use the Gulf.