The Pentagon officially acknowledged yesterday that the results of a secret exercise called "Nifty Nugget," conducted almost two years ago to see how fast the United States could mobilize at home to fight a war in Europe, were not very nifty.

"Though many parts of the mobilization process worked well," a Pentagon report said, "the exercise revealed significant difficulties and shortfalls that have to be resolved if we are to reinforce the European theater" of operations.

The exercise made it clear "that existing mobilization plans were a hodge-podge of old and unconnected president emergency orders, policies, regulations and procedures," the report concluded.

Many of the civilian government agencies that are supposed to help in a military emergency did not know what to do, nor did the Pentagon know what these other organizations were supposed to do, it indicated.

Nifty Nugget, a simulated exercise, was carried out in October 1978.No reserves were called up. No tanks were put on ships. In fact, no one knew about the operation except for about 2,000 military and civilian officers in about 30 federal agencies who went through the motions of putting the country quickly on a war footing after a supposed attack with little warning by Soviet-led Warsaw Pact forces against Western Europe.

The exercise was so encompassing, however, that Undersecretary of Defense Robert W. Komer called it "the most ambitious test of mobilization ever undertaken in this country, and perhaps the world."

In a statement accompanying the report, Defense Secretary Harold Brown warns readers that the results reflect the situation two years ago, rather than today. The results, he says, have been used to make changes, and more will be made in preparation for a second major test later this year.

Though military analysts believe that a war in Europe would not come as a total surprise, but rather after growing tension, the repeort warns that "the penalty for being unprepared for a surprise attack is so great that we have no choice in our planning but to assume its occurrence."

Military specialists have long worried not only about detecting warning signals of an attack but also about whether a U.S. president or leaders of the NATO allies would decide to mobilize in a timely fashion even if they had indications an attack was brewing.

One objective of the 1978 exercise was to demonstrate how that warning time could best be used.

The report released yesterday is an unclassified version of the results and therefore deals mostly with bureaucratic problems.

It does not include any military assessments of what would have happened to U.S. troops on the battlefield. It can be assumed, however, that the story would have been bleak because of the shortages in everything from ships to carry reinforcements, to doctors to treat the wounded.

Among the published findings:

"All services reported significant shortages in important air and ground weapons delivery systems, armored combat vehicles and essential space parts." A separate analysis of the ability of U.S. industry to quickly meet a surge in military demands "indicates that industry probably cannot provide additional new equipment during the early months of a short-warning conflict."

There was a need for better planning and management of the U.S. airlift and sealift intended to ferry troops and equipment overseas. Lack of flexibility "caused unnacceptable delay in the movement of units and supplies. . .," the report said. The shortage of aircraft space parts made things progressively worse.

Serious shortages of trained reservists forced the Army to strip combat-skilled personnel from some of the late-deploying units to fill other ranks. The pool of individual ready reservists, the report said, "is well below the level needed, at least by the Army," to bring active and reserve units quickly up to wartime manning levels and to provide replacements for casualties.

At the time of the exercise, there was no single document that laid out for the secretary of defense all the operational objectives for the mobilization plans put to the Nifty Nugget test. There was also "no comprehensive document" describing for the executive branch the available options in such an emergency.

There was no federal coordinator to integrate plans for receiving non-combat causualties, and many government agencies did not know how many of their employes were reservists and thus might be called up, leaving their civilian roles unfilled.