UNDERSTANDABLY, Congress wants a larger voice in United States policy in the Gulf. The potential for US involvement in the Iran-Iraq war, which entered its eighth year this week, grows with the presence of each added ship in the waterway. President Reagan says any invocation of the 1973 War Powers Resolution by which Congress might set a cutoff date for withdrawal of US troops from the Gulf would be a ``big mistake.'' Yet it can also be argued that the administration is making a ``big mistake'' in ignoring the importance of a broadly supported, bipartisan foreign policy in the Gulf. It is Congress that votes the money for such ventures and takes much of the heat when lives are lost. Two-thirds of Americans, according to a recent CBS/New York Times poll, think President Reagan should get congressional approval to keep US ships in the Gulf.
In an era when war is rarely formally declared, the war powers legislation is virtually the only way Congress can exert the kind of authority over the conduct of hostilities intended by those framing the US Constitution. It is the Supreme Court which one day must decide if the resolution is an invasion of the President's authority as commander in chief. So far both Congress and the White House have avoided the kind of confrontation that might trigger such a legal ruling.
The UN Security Council's bid for an Iran-Iraq cease-fire has strong international backing. Iran, for a mix of reasons, including its long-held desire to oust Iraqi leader Saddam Hussein from power, resists. Yet Iran President Ali Khamenei, while calling punishment of Iraq as the war's ``aggressor'' his nation's highest priority, insists that Iran has not closed the door to negotiations.
The UN Secretary-General's recent trip to Iran and Iraq, while yielding no concrete results, was both important and necessary; it may not have narrowed the differences between the adversaries, but it defined them more precisely.
Clearly there is more unity now among Iran's top leadership, and Tehran has hinted that it might settle for an undeclared cease-fire as an impartial tribunal simultaneously takes up the question of who started the war.
Iraq, which prefers the Security Council proposal that calls for an inquiry after a cease-fire takes effect, is concerned that blame could lead to reparations.
Each side frets that the other will build up its forces during a cease-fire.
The US, wary of Moscow's increased involvement in the Gulf, resists the Soviet proposal for an international peacekeeping force. The Reagan administration is correct that practical problems would follow: The UN has no naval force, and decisions would be needed on who would participate in and control the effort. Yet some variation, such as a rotation of escort operations, at least among Western nations, should be possible.
The US is not as alone in the Gulf as it once was. France and Britain have ships there; a small number from Italy, the Netherlands, and Belgium will soon arrive. Europeans have also sharply cut back on arms sales to Iran. And Britain last week, after an Iranian attack on one of its tankers, shut down Iran's military procurement office in London, which coordinates European purchases.
Yet international arms sales are a big business, notoriously hard to control. Iran buys much from North Korea and China and, by some estimates, makes as much as three-fourths of its own weapons. The US has been pushing extremely hard, and as yet unsuccessfully, for a Security Council embargo on arms to nations failing to heed the UN call for a cease-fire.
Even if such an embargo were adopted, the practical effect would likely be slim. The problems of policing it and determining who is cheating could be considerable.
Wisely, the US has cooled its pitch for an arms embargo in recent days. Washington cannot afford to be too far ahead of the pack.
The Reagan administration could well afford a similar distancing in its tendency to self-congratulation in the recent US seizure of the Iran mine-laying ship. The prompt display for photographers of temporarily captured Iranians, prone on the deck with hands tied, stirs memories of similarly tasteless Iranian displays of US ``prisoners'' during the hostage crisis.
Iranian words and deeds may appear totally irrational by US measures. But by continually calling Iranians barbarians and terrorists, the US heightens the tension between Washington and Tehran.
In the long run Iran may not prove to be Washington's principal adversary. One-time adversaries have a way of becoming allies. Putting Iran in an impossible position will benefit only Moscow.