Reagan administration officials said yesterday that there is disagreement on how to interpret informal Soviet suggestions in Geneva last month that Moscow is prepared to cut its proposed overall ceiling on European intermediate-range nuclear weapons below 300 by 1990.

The Soviets have also hinted at willingness to limit the number of SS20 intermediate-range mobile missiles within that total to fewer than 160, administration sources said.

The Soviets have also talked of a geographic zone within which these reductions would be made and where limitations would be effective, but no precise definition of the zone has emerged, the sources said.

Soviet negotiators "hinted at" such proposals "in bits and pieces" during informal meetings with U.S. counterparts in the closing weeks of the recently recessed round of talks in Geneva on European-based nuclear arms, one source said yesterday. The ideas were "never formally presented in the negotiation sessions," the source said.

One group of administration officials believes that the newly offered ideas "represent an opportunity for a breakthrough" that should be taken into consideration as negotiating instructions are drawn up for the next round of talks scheduled Jan. 27.

This group wants to explore the Soviets' ideas further and points out that the proposed SS20 reduction would be from the present European deployment of more than 200. The Soviets would maintain 100 more SS20s in the eastern Soviet Union aimed at China and Japan. This group also believes now is the time to begin exploring alternatives.

Another group, however, sees nothing new in the ideas, which, as one official said yesterday, "would still leave us with zero missiles and the Soviets with more nuclear warheads than they need."

The official pointed out that by 1990, half of the missiles the Soviets say they are willing to cut will be too old to be operational. The 160 missiles that would be allowed the United States under the new Soviet concept would be accounted for by the 162 currently deployed by the British and French, according to the Soviets' way of counting, he said.

This second group believes that the Soviets will not negotiate seriously until they are certain that the new U.S. Pershing II and cruise missiles will be deployed. They are scheduled to be deployed beginning next December.

Publicly, the administration has been firm in supporting the "zero option," under which the Soviets would dismantle all intermediate-range nuclear missiles while the United States would cancel deployment of proposed new missiles. An administration official told United Press International yesterday that "there has been no change in the president's position."

The disagreement within the administration about what the Soviets intend by their suggestions reflects a deeper split between officials on whether the United States should now move away from its initial "zero option" position.

Even administration officials who want to pursue negotiations believe that if the Soviets retain any European-based SS20s, the United States must deploy a roughly equal number of either Pershing IIs or cruise missiles, or a mixture of both.

The U.S. goal before the talks began last December was to focus solely on missiles. The Soviets had older ones, SS4s and SS5s, and the newer SS20s. To meet the SS20 threat, the North Atlantic Treaty Organization had agreed to the Pershing II and ground-launched cruise missile deployment next December.

The Soviets have strongly opposed introduction of these missiles into Western Europe, primarily because they could quickly hit targets inside the U.S.S.R. The Pershing IIs, for example, would take about eight minutes from launch to impact.

Under the "zero option," the Soviets were to dismantle all 324 SS20s and 260 SS4s and SS5s. In turn, the United States would cancel deployment of 108 Pershing IIs and 464 ground-launched cruise missiles.

Under the initial Soviet proposal, both sides were to reduce current intermediate-range nuclear systems, which included bombers and sub-launched and ground-launched missiles, to 600 by 1985 and 300 by 1990. By its count, Moscow declared in February that each side currently had about 1,000 such systems.

But as U.S. officials are quick to point out, the Soviets included not only British and French nuclear systems, but also American nuclear-capable fighter-bombers. On the Soviet side, however, they left out more than 1,000 such fighter-bombers.

Within those numbers of systems allowed under the initial Soviet plan, each side could choose freely among various types of systems.

During the first two rounds of talks in Geneva, little progress was made beyond each side laying out what was embodied in each proposal. However, in the third round, which began Sept. 30 and ended Nov. 29, some U.S. officials believe progress was made.

They described the hints about reducing overall limits and establishing missile sublimits as "important" and said they believe the next round could bring a breakthrough if U.S. negotiator Paul H. Nitze is given leeway to explore agreements outside the "zero option".

Some officials expect that top officials of the new Soviet government may embody the new ideas next month in major speeches aimed at influencing the West German electorate, which votes on a new government March 6. Deployment of Pershing II and cruise missiles in Germany is a controversial issue.