The Soviet Union, responding to Reagan administration requests, proposed for the first time yesterday a detailed draft treaty calling for sharp reductions in strategic nuclear weapons, according to U.S. officials.

State Department spokesman Charles E. Redman welcomed the move as "a step forward" in the strategic arms negotiations under way in Geneva, but he and others indicated it lacks any concessions on major, long-disputed issues.

Chief among these disputes is a Soviet demand that the strategic arms reductions be delayed until the United States agrees to limitations on the testing and deployment of space weapons, which the Reagan administration has resisted.

"The Soviet treaty incorporates the same unacceptable linkage that would hold hostage . . . arms reductions to measures that would in effect kill" the U.S. Strategic Defense Initiative (SDI), or "Star Wars," program aimed at developing a comprehensive ballistic missile defense, Redman said.

The Soviet move comes amid a flurry of other arms-control initiatives, including an agreement by Soviet leader Mikhail Gorbachev on July 22 to give up medium-range and short-range missiles in Asia, and the introduction in Geneva Wednesday of a detailed Soviet proposal for agreement on space weapons limitations.

"The Soviets finally realized they had to move forward with us or risk looking bad," said retired lieutenant general Edward L. Rowny, a senior U.S. arms control adviser. The United States introduced its own version of a strategic arms treaty two months ago, he noted.

But several officials here cautioned yesterday that the two sides remain much further apart on strategic arms and space weapons than they do on the topic of medium-range and short-range missiles, raising questions about reaching agreement on strategic and space weapons in the remaining 1 1/2 years of President Reagan's term.

One of the sharpest differences concerns a U.S. request for tight constraints on the number of offensive nuclear warheads atop ballistic missiles. The Soviet Union, which has more than 90 percent of its nuclear arsenal atop land- and submarine-based missiles, has termed the U.S. demand unfair.

Another sharp difference involves a Soviet demand for a ceiling of 400 long-range, nuclear-tipped, sea-launched cruise missiles on each side, to be deployed only on submarines. The administration, which plans to deploy several thousand such missiles with either nuclear or conventional warheads on submarines and surface ships, has resisted such a ceiling on the grounds that compliance probably could not be verified.

The United States also has proposed to ban all mobile ballistic missiles, including the Soviet's SS25 missile now being deployed and SS24 missile nearing deployment. The Soviets, in contrast, would include these missiles and the U.S. Midgetman mobile missile under development in a ceiling of 6,000 warheads and bombers on each side that was agreed upon last year. The United States now has roughly 11,800 warheads; the Soviets, about 10,000.

The Soviets want the reductions to occur in five years; the United States wants seven years. The United States wants to limit the total lifting power of ballistic missiles, while the Soviets have resisted any direct limitation on the grounds that planned cuts in their large SS18 missile force would have the same effect.

U.S. officials said that absent any new Soviet concessions, the most that U.S. negotiators can do is try to combine the two draft treaties and highlight the areas where disagreement persists. U.S. negotiators will propose this next week, the officials said.