THE UNITED STATES' widening trade deficit means trouble. It is currently running at a rate of about $70 billion a year, an unprecedented level. As the secretary of commerce, Malcolm Baldrige, observed, it could increase to $100 billion next year. But the important thing to remember is that this trade deficit is a consequence, not a cause.

It is a consequence of the very high exchange rate of the dollar, at a time when the American economy is finally recovering from the recession. The high exchange rate is, in turn, a consequence of high interest rates, which, to follow the chain of causes back to the basic one, are the result of the enormous American budget deficit. People who are unwilling to do anything about the budget deficit are in no position to complain about its inevitable effects.

There is temporarily a silver lining of some importance to this trade imbalance. The American economy, as it accelerates, is sucking in imports from the rest of the world at a pace that helps their own economies grow. That's a valuable contribution while it lasts --but it would be dangerous to let it last long. If the present imbalance were to continue through 1984 on the scale that Secretary Baldrige suggests, it would generate formidable protectionist pressures in this country. Equally ominous, it would mean that a rising share of the world's capital was being devoted to financing the American budget deficit.

The Reagan administration has occasionally noted with satisfaction that the inflow of capital from overseas makes it easier to borrow the money to cover the budget deficit. That's true, but the money has come disproportionately from countries--notably Latin America and France--that are themselves heavily indebted and in dire need of capital.

The implications of the huge trade imbalances now in prospect, if they persist through the coming year, are unpleasant. They include increasing instability in an overstrained monetary system, sharp fluctuations in exchange rates and disruptions to stable economic growth worldwide. But don't blame trade, or the trade figures. Look back to the real source of the trouble-- the $200 billion-a-year budget deficit that represents the difference between all that Americans want from their federal government and what they are willing to pay for it.