AWACS IS BACK - the billion-dollar-plus airborne warning and control system (seven planes) that the administration wishes to sell to Iran. Congress gagged on the proposal last summer, but the President has now trimmed some of the deal's most objectionable features. Greater assurances against loss of sensitive equipment to Soviet espionage are now offered; Iran will be under tighter pressure to hew to defensive rather than offensive purposes; the numbers and roles of Americans, potential hostages to in voluntary American involvement in Iranian trouble, will be restricted. The President argues that as a bulwark of regional power, a major oil supplier and a traditional friend, Iran is worthy of AWACS. Unless both houses of Congress vote against it promptly, the deal will go through.

Headcounters expect the administration to win handily. To go against the President on AWACS a second time, when he has taken conspicuous if not full steps to answer earlier questions, seems to be more than most legislators want to take on. What with Panama dominating the fall foreign-policy agenda on Capitol Hill, there is not much disposition to go to the mat on Iran. It can plausibly be argued that the new systems of congressional review of executive arms deals - the system that allowed Congress to get into the act - has worked fairly well in this case.

But we still like the AWACS deal. There are good political and economic reasons for the United States to maintain its friendship with Iran. Nonetheless, the sale introduces an exotic and possibly provocative technology into a volative region. It is right on the borderline between systems sold because of the buyer's insistent political demand. The sale is, on the whole, an embarrassment to Mr. Carter's professed intention to reduce the American role as the leading arm merchant in the world.

The whole AWACS episode suggests that, by the time a deal gets to the stage of congressional review it is too late to do much about it. It is earlier, when seller and buyer consult quietly about the whole supply relationship, that restraint and a sense of proportion must be applied. The United States is selling $11 billion worth of arms this year. Iran is buying $6 billion. Those numbers raise a red flag.