Secretary of State George P. Shultz gave foreign ministers of the North Atlantic Treaty Organization a detailed description today of U.S. planning for his talks next month with Soviet Foreign Minister Andrei Gromyko and promised that America's allies would be consulted extensively about the move toward new arms-control negotiations.

But senior U.S. officials said that throughout the 4 1/2 hours of highly secret discussion, Shultz stressed repeatedly that President Reagan has not yet made the major decisions about U.S. strategy for his meeting with Gromyko in Geneva next month.

According to the officials, Shultz also reiterated that the Geneva talks will deal less with the substance of arms control than with procedures for how to deal with the three distinct areas of strategic nuclear missiles, medium-range nuclear missiles and space weapons.

European sources described Shultz as saying that the United States wants a "frank dialogue" and intends to approach the talks in a "positive, extremely serious and open-minded manner."

However, both European and U.S. officials said, Shultz cautioned that any negotiations will be long and difficult. He also said that the difficulty in perceiving Soviet goals and motivations makes it impossible at this stage to predict whether the negotiations will lead to arms control agreements.

Those parts of Shultz's hour-long presentation to the NATO ministers that were made public essentially were a reiteration of points that the Reagan administration has been stressing since the Thanksgiving Day announcement of the meeting to be held Jan. 7 and 8 in Geneva.

Although Shultz is known to have revealed some of the negotiating ideas that the administration has under consideration, officials of the 16 NATO member countries refused to make them public.

Instead, they said, there is a general recognition within the alliance that U.S. planning is still in a highly tentative stage, and the main emphasis at today's meeting was on reassuring the Europeans of Washington's intention to consult and inform them fully.

The West Europeans are especially concerned about those negotiations aimed at reducing medium-range missiles. The 1979 NATO decision to deploy 572 U.S. cruise and Pershing II missiles in Western Europe has caused great controversy, and allied leaders are anxious to reassure people in their countries that the West is doing everything possible to engage the Soviets in agreements that will ease the likelihood of nuclear confrontation on the continent.

West German Foreign Minister Hans-Dietrich Genscher, president of the meeting, summed up the European concerns by citing the need for "close consultation and coordination, marked by mutual trust between Europeans and Americans." The same point was made repeatedly by all the other ministers during the lengthy, closed-door discussion.