MOSCOW, OCT. 19 -- Two months before the introduction of major economic changes in the Soviet economy, key industrial sectors are lagging behind their 1987 targets, top Soviet planners in the Kremlin said today.

Despite the slowdown in industrial growth, the 1988 budget presented to the Soviet legislature calls for even higher goals that some western analysts said could place unrealistic demands on the reform program.

"It seems they have given in to the temptation of setting ever higher goals," said one western diplomat. "If they would give themselves a breather, I would be more sanguine about the success of perestroika," or the restructuring program, of party leader Mikhail Gorbachev.

According to the budget announced today, the targeted increase in industrial output for next year is 4.5 percent, compared to the still-unrealized figure of 4.4 percent for 1987. Economic statistics released over the weekend showed that industrial output grew only 3.6 percent over the first nine months of 1987, compared to 5.1 percent during the same period last year.

Some areas of the economy continued to post strong performances -- in particular, energy and agriculture -- but the machine-building and light industries again have failed to meet their targets. These two areas, considered key to the economic drive launched by Gorbachev, were criticized in a speech to the Supreme Soviet today by the top Soviet planner, Nikolai Talyzin.

"Certain difficulties have arisen this year in the machine-building industry," said Talyzin, who heads the state planning committee, Gosplan. "The economy is not receiving a considerable amount of the equipment it requires." He noted that construction time is still twice what it should be and that many enterprises continue to seek money from the government to keep afloat.

These old, but persistent, problems are likely to dog Soviet economic performance again next year, when 60 percent of Soviet industry switches from a system of centralized planning to a more decentralized, self-financing arrangement that gives local managers greater autonomy.

Finance Minister Boris Gostev said today that the 1988 budget was based on "a fundamentally new financial policy" that included the redistribution of "more than 100 billion rubles" ($156 billion at the official exchange rate) back to the enterprises. He did not elaborate on how the money would be used.

Figures released this week showed that the new quasiprivate cooperative sector is beginning to take off, with more than 8,000 cooperative enterprises, employing more than 80,000 people, at work as of Oct. 1. The growth of this sector is considered another key part of Gorbachev's reforms.

In presenting the 1988 budget, Gostev admitted that the publicly announced portion of the defense budget -- 20.2 billion rubles, or 4.6 percent of the budget -- was limited to "upkeep of {military} personnel, payment of pensions, military contruction and other expenditures."

Omitted from Gostev's statement were procurement and research and development -- which western military specialists have considered for years to make up the bulk of real Soviet defense spending, estimated by some westerners to be 13 percent of the budget. Gostev's statement was seen as a first step toward a more frank public accounting of Soviet military spending.

Gostev also revealed that cutbacks in alcohol sales had cost the state treasury 12 billion rubles, more than half the amount of alcohol profits for the state during the 1970s.

The loss of what are popularly called "drunken rubles" has been compounded by losses from goods rejected as defective by the new state quality control agency, Gospryomka. According to recent reports, in the past nine months Gospryomka has rejected products worth 42 million rubles.

Soviet economic problems have been further strained by a drop in foreign trade, attributed to the decline in world oil prices. According to published figures, Soviet foreign trade fell 3.6 percent from last year, with exports down 0.5 percent and imports down 4.2 percent.

Although total agricultural production grew by only 1.1 percent over the same period last year, meat, milk and eggs showed strong growth. Talyzin today set next year's target for grain production at 237 million tons, 5 tons more than this year's plan.