A top Common Market official yesterday delivered a bleak assessment of prospects for the successful conclusion of the multilateral trade negotiations (MTN) going on in Geneva.

Sir Ray Denman, director general of external relations for the European community, told a news conference at the State Department that the proposed package of reduced tariffs and trade barriers offered by the United States and other nations is "not sufficiently balanced" to enable European negotiations to recommend its adoption.

Denman, along with the chief European negotiator, commission vice president Wilhelm Haverkamp, has been here for the 17the semiannual consultation with American officials on and a whole range of specific economic problems. Havekamp met Tuesday with President Carter for a brief general discussion of trade, energy and other issues.

Undersecretary of State for Economic Affairs Richard Cooper said, in reviewing the global economic outlook, that "for the world as a whole, 1979 will be some what better than 1978.

He said there would be a further slowdown of economic growth here and an acceleration of growth in Europe, which would tend to restore a better balance in international payment accounts.

Denman made clear that a major stumbling block to the MIN is the expiration on Jan. 3 of a waiver in existing law that enables the United States to refrain from imposing countervailing import duties, as an offset to export subsidies paid by European countires.

Without the waiver, some $500 million in European exports to the United States, especially food products from Denmark might be disrupted.

In a recent round of conferences in Europe, U.S. special trade negotiator Robert S. Strauss assured his opposite numbers that the Carter administration will do everything it can to extend the waiver.

But Cooper yesterday summed up the Common Market's response to Strauss' assurances by saying "the community's raction was that that's very nice, but it's not sufficient."

In an interview earlier this week, Strauss said he was still hopeful an agreement would be reached before the end of the year, but warned that the MTN would not be a cure-all for world economic problems in general, or the U.S. trade deficit in particular.

Denman said that Europe's desire for a firm extension of the waiver did not preclude "an understanding" in advance of such an extension that would enable the negotiations to continue, but said firmly "we are no prepared to conclude the negotiations" until the waiver extension is a reality.

Although the Carter Administration would like to look the other way, Cooper conceded yesterday that without the waiver there is no legal way the countervailing duties can be suspended. Byt he held out the possibility that the secretary of the Treasury "might not actively collect the duties imposed" if importers assure the Tresury they will pay the duties if they are eventually assessed.

Congress, meanwhile, which must eventually vote an MTN agreement up or down, might find it difficult to deal with a European agreement conditioned on extension of the waive.

But beyond the procedural Catch 22 situations, there are importat substantive disagreements between the United States and the Common Market that needed to be ironed out prior to the Dec. 15 deadline set by the Bonn Summit, which now is to be followed by a Dec. 19 European council meeting.

Denman said there had been "some spirited and vigorous conversations" this week with U.S. trade representatives, "and we have some hot negotiating to do . . . if we are to bring this to a successful conclusion."

The European official, in explaining the lack of "balance" in the package, said the Common Market wants greater reductions in U.S. industrial tariffs, especially on chemicals and textiles. There is also a wide area of disagreement on agricultural subsidies.

Another touchy area is the European demand for amendment of the General Agreement on Trade and Tariff (GATT) rules so as to establish "selective safeguards" against excessive imports. These would allow importing nations unilaterally to discriminate against individual exporting countries.

Denman said the Common Market wants "a facility that would allow us responsibly, but effectively enough to prevent trade disruption in the 1980s."

The United States, while recognizing that some "selective safeguard" provision is reasonable - one that it might also want to use - has been seeking some international control of its application.

In response to questions, Denmane said that GATT rules need to be changed because of "expotential increases in exports" from lowest producing countries. He said Europe wants "the possibility of taking selective action, not clobbering the whole world to deal with the particular sources of trouble."