UNCERTAINLY AND SLOWLY, this country is trying to make up its mind about foreign trade and the proper American position in world competition. The national state of ambivalence, in all its awful complexity, is accurately reflected in that gigantic heap of legislation known as the trade bill. As both House and Senate have passed it, the bill contains several useful provisions -- and much mischief.

At the moment the bill isn't making much progress. The conference committee has formally begun its work, but in fact most of the key people have been occupied with the budget, and nothing much is happening on trade. It wouldn't necessarily be a misfortune if this bill moved slowly.

It is the product of a period in which the United States was reaching around anxiously for ways to cut off the rising tide of imports. But that time is already ending. The principal cause of the trade deficit, the excessively high exchange rate of the dollar, has been corrected. American manufacturing efficiency is rising rapidly. American exports are starting to increase. This country was running a trade surplus as recently as 1981 and, if it is to keep its foreign debts under control, it will need to run a surplus again in the 1990s. If its expanding imports in the next decade were to run into a new array of antitrade laws abroad, modeled on a bill passed by Congress in 1988, that would be a great misfortune for the United States.

The Reagan administration is now working diligently to broaden the world's trade rules, known as the General Agreement on Tariffs and Trade. But there are at least half a dozen provisions in either the House or the Senate version of the trade bill that would be illegal under the GATT. A lot of people in Congress have lost patience with the GATT's slow process of negotiation. They have fallen into the habit of attributing the trade deficit -- inaccurately -- to unfair practices abroad. They want to impose American standards -- most of them written to help industries that want protection from imports -- and tell the rest of the world to accept them or else.

It won't work. The United States sets the pace in trade, and if it begins closing the door on imports it can expect the rest of the world to follow its example. The conference committee would be right to take as much time as it needs to revise the bill for a time in which American exports are going to be rising steadily and access to foreign markets will be essential to this country's economic growth. If the conference committee can't do that, the country will be better off with no trade bill at all.