NATO commander Gen. Alexander Haig today unleashed an all-out verbal attack on the Soviet Union, charging that Moscow and the "totalitarian regimes of the East bear a large measure of responsiblity for this international disease" of terrorism and unheaval "with which we are all plagued to day."

The four-star general, addressing first a press conference and then a farewell ceremony just hours before he officially hangs up his uniform after 31 years of U.S. Army service and 4 1/2 years as the supreme allied commander in Europe, also spoke of unnamed "virulent forces" seeking to promote change through violence and terrorism and of "Soviet paranoia" over the emergence of China as a modern power.

Haig's comments went far beyong those traditionally expected of military officers and undoubtedly are a preview of the line he will espouse as he enters civilian life and a possible shot at high political office.

The one-time top aide to former president Richard Nixon and secretary of state Henry Kissinger has been mentioned in some conservative circles as a possible presidential or vice presidential candidate or contender for a Senate seat from his native Pennsylvania. Today he repeated that "as of now, I have no political plans.

"When I return home, I intend to speak out publicly on the concerns that I depart here within the security area. I will assess the productivity of such public statements and continue them or terminate them depending on the contribution they do or do not make," he said.

Just four days ago, Haig, 54, narrowly escaped an apparent assassination attempt when a bomb blew up under a bridge as his car was crossing it. Today, at his press conference, he seemed somewhat emotional and combative, his voice rising sharply and falling to emphasize points.

At one point, after a long answer to a reporter who wondered what the effect of Western support of dictators in Iran and Nicaragua had no global upheaval, Haig said, "If that doesn't answer your question, then think about it for a while."

Haig said he hoped that terrorist activities could be halted through East-West negotiations. Yet, he went on, "thus far we have observed an unwillingness on the part of the Soviet Union to abandon its philosophical approach to historic change. That it, to permitit to proceed within the confines of the accepted rules of international law."

"And we have also seen an unwillingness, as recently as the Vienna summit meeting" just concluded between Presidents Carter and Brezhnev, "for the Soviet leadership to abandon its stated right to support liberation movements under whatever guise they appear . . . even when it occurs in areas of vital interest to the Western and free world."

Although Haig is viewed as certain to join the opponnets of the new strategic arms treaty, he declined today to "make a public value judgment" until he had an opportunity to "intensely study" the treaty provisions.

"For me, the bottom line will be whether or not the United States is going to be better able to do what we must do in the face of the changing strategic balance, with SALT II or without it."

Haig said it was "my firmly held conviction that the rhetoric, promises and atmospherics" of detente, one pillar of Western policy, "can never be a replacement for the unity, will and continued military readiness of our deterrent pillar."

A crucial point to consider, he said, was the "worsening balance" for the West of opposing nuclear forces in central Europe.

Haig was replaced here today as NATO chief by Gen. Bernard W. Roggers, the 57-year-old former Army chief of staff.

Haig has probably been at the center of political-military power in the United States longer than any one serving today. And, although he is respected throughout NATO as one of the mostforceful and effective commanders in the alliance's 30-year history, many observers view his political chances, if he harbors real hopes, as slim.

Senior Army officers here and some political observers in Washington feel Haig has no real constituency at home, is not a war hero as was Gen. Eisenhower, lacks the touch and language for contact with civilians and has too little time to build support.

Some others, however, believe that the Haig, fresh out of uniform, could have a dramatic impact on the SALT debate at the very least and might wind up as the candidate of a deadlocked group of conservatives. CAPTION: Picture, Gen. Haig, right, shakes hands with Gen. Rogers, his successor as NATO head. UPI