The Constitution is unambiguous: Congress alone "shall have power . . . to declare war."

About the facts, however, American practice is equally clear and contrary.From Jefferson's dispatch of the Navy to protect American shipping from the Barbary pirates to President Bush's buildup of troops in preparation for offensive action against Saddam Hussein in the Persian Gulf today, presidents have employed U.S. military forces abroad without prior congressional approval or declaration of war.

Of the conflicts known to us as "wars," three of the most costly in both lives and money - the Civil War, Korea, and Vietnam - have been undeclared and waged largely on presidential authority, with Congress at best an after-the-fact ratifier of presidential initiatives.

No serious person should doubt that the president can order American troops into action in the Persian Gulf without any further action by Congress. The issue is whether he would be wise, and the country well-served, to require Congress to stand up in support of the U.N. Security Council resolution, or stand down.

The reasons presidents have shied away from Congress in making decisions about war are not difficult to discover.

First is time. When Saddam Hussein invaded Kuwait, Congress was in recess, as it had been at the outset of the Civil War, and immediate choices were required.

A second is flexibility. When standing eyeball to eyeball with an adversary, whether Kennedy with Khrushchev over missiles in 1962 or Bush with Saddam today, any commitment to others forfeits maneuvering room.

Flexibility is compounded by uncertainty. Will Saddam withdraw or not? If he were to withdraw to northern Kuwait and propose to negotiate, what then?

Uncertainty is compounded by complexity. To marshal our forces, deploy them, control them, persuade allies, maintain an international consensus, win authorization from the U.N. Security Council, all the while trying to communicate effectually with Baghdad - such a load constitutes a staggering burden on men already encumbered by innumerable governmental tasks.

But what then of the constitutional intent that recourse to war should require a collaborative judgment by the whole body of national elected officials. What about Congress?

In the wake of Vietnam, Congress sought to reclaim its role by passing the 1973 War Powers Resolution - over President Nixon's veto. This law requires the president to explain the causes for any military action to Congress within 48 hours and to terminate U.S. involvement unless Congress approves the action within 90 days.

Five presidents have judged this law unconstitutional. No president has submitted any report on military activity or impending hostility to Congress under the terms of this resolution. Nor is President Bush likely to do so.

In the aftermath of this crisis, Congress should accept the fact that however worthy the objectives, the War Powers Resolution is not working and is not workable. It should be repealed in favor of a more operational, viable alternative.

The right starting point for reconstruction of a more satisfactory arrangement is the constitutional presumption that collaborative judgments of the president and Congress will, on the average, produce better assessments of the costs and benefits of war than any alternative.