WASHINGTON (AP) _ President Bush has the power during national emergencies such as wartime to try to stop a strike or lockout if it threatens the nation's safety.

Under a provision of the National Labor Relations Act, the president can appoint a board of inquiry into a labor dispute when there is a national emergency.

For the provision to be invoked, the dispute must ''imperil the national health or safety'' and involve all or a substantial part of an industry.

There was no discussion about Bush invoking the provision during a week- long strike at a munitions plant in Minneapolis. Striking workers there, who make 25-millimeter shells for the Persian Gulf War, voted to accept a new contract Sunday.

If a labor dispute is considered a peril, the president can direct the U.S. attorney general to petition any federal district court to stop the strike or lockout once the board of inquiry's investigation is complete.

Federal law did not address labor disputes in times of national emergency when World War II started, so then-President Franklin D. Roosevelt convened a labor-management conference to suggest ways to avoid labor disputes so that war production would not be disrupted.

That conference agreed to reciprocal no-strike, no-lockout pledges and to the creation of an 11-member National War Labor Board with powers to mediate, conciliate and arbitrate disputes. The board was disbanded after the war, but federal labor law was later enacted to ensure there were ways a president could intervene.

Since the Persian Gulf War began Jan. 17, there have been only a few labor disputes that had the potential of affecting the war effort.

The Minneapolis strike involved about 1,300 employees of Alliant Techsystems Inc. The company said during the strike that production would not be hindered and workers said the war was not an issue in the walkout, but U.S. Army officials monitored the negotiations.

Army spokesman Al Schwartz at the Army's Armament, Munitions and Chemical Command in Rock Island, Ill., said that if a delivery problem had arisen from the Minneapolis strike, the military could have awarded Alliant's contracts to another company or asked Bush to step in.

Last week, the nation's major freight railroads and its labor unions agreed to a two-month extension of contract talks, largely because neither side wanted a disrupting nationwide rail strike in the middle of war.