Gen. Alexander M. Haig Jr., holding himself out as a promising replacement for President Carter in 1980, yesterday lambasted the administration for "impulsively" ruling out the use of force against Iran in the early stages of the crisis.

"The worst thing we can do in one of these situations where there is lawlessness is to suggest at the outset that we reject the option of force," the recently retired commander of the North Atlantic Treaty Organization told reporters at a breakfast here yesterday.

President Carter introduced the threat of military intervention Tuesday for the first time in the 18-day-old confrontation.

Haig, a protege of Henry A. Kissinger who played a crucial role in the Nixon White House, took broad swipes at the defense policies of Carter and Defense Secretary Harold Brown, and outlined what he called the devastating decline of America's image in the face of a Soviet buildup. He acknowledged that Watergate and other pre-Carter events had contributed to that "decline."

Haig blamed the Carter approach for the fact that the nation is "less than well-structured" to carry out certain types of military operations in the Middle East if necessary. The United States would be "hard pressed," he said in response to a question, to put into Iran more than one division in less than 45 days.

Haig declined to recommend a particular course of action, however, and cautioned that there are limits on the use of force not just because of short-term practical problems but also because of possible long-term effects on what he called radical Arab movements.

Haig also said the administration had muddled U.S. relations with European allies to the point that they are not offering the U.S. much support in the current crisis, even though it is clearly in their interests to do so.

In civilian clothes Haig retains his air of command. He periodically stabbed the air with his finger, fixed his listeners with a steely blue-eyed gaze and raised his voice aggressively.

When someone asked him if he might not have his eye on a Senate seat, rather than the presidency, he snapped, "i'm not a committee man,"

Haig acknowledged the limits of his potential as a viable candidate, even as he brushed aside the widely held notion that he is actually shooting for the vice presidency, or the Senate seat of Richard S. Schweiker.

"I think I am as promising a national candidate as there is in the field," he said, " and the least nominable."

He indicated that erstwhile colleagues such as Kissinger, Gerald R. Ford and Richard Nixon share both those sentiments.

Haig repeated an earlier statement that he had no political plans when he resigned his NATO post last summer, but he said he has felt increasing pressure from supporters, notably a national draft-Haig committee and concentrations of veterans in some states, to join the field of Republican contenders.

He said he will announce a final decision within a few weeks.

His strategy, such as it is, is to write off the initial primaries, including New Hampshire, and focus on Florida, New Jersey and his home base, Pennsylvania.

Haig's Pennsylvania base and the fact that he is a Catholic enhance his desirability as a running mate for the Republican nominee.