The Soviet Union has turned down an American request for a special session of the U.S.-Soviet Standing Consultative Commission to discuss Reagan administration concerns that Moscow may be violating strategic nuclear-arms agreements, according to U.S. officials.

The officials said the Soviets claimed that they were not violating past agreements and offered some explanations about the disputed activities.

The Soviets suggested that the United States could raise whatever concerns it had at a regularly scheduled session of the commission late this month, according to the officials.

The officials said the preliminary Soviet explanations about the alleged violations were unsatisfactory and that U.S. delegates to the next session are certain to pursue the explanations. Secretary of State George P. Shultz also may bring them up in his meeting next week in Madrid with Soviet Foreign Minister Andrei A. Gromyko.

The initial U.S. request to Moscow for a special meeting was made in July and the Soviet response came in August, the U.S. officials said in response to inquiries made before a Soviet fighter apparently shot down a South Korean airliner last week.

The U.S.-Soviet commission, which holds regular meetings twice a year, was set up in 1972 to monitor adherence of both sides to the first strategic arms limitation agreement (SALT I) and the anti-ballistic missile (ABM) treaty that both signed that year.

Soviet rejection of the U.S. request for a special meeting reportedly has caused debate in the White House, with some officials pressing for President Reagan to make another public statement about the alleged Soviet violations, while others prefer to handle the problem quietly until more can be learned about the disputed Soviet activities.

Among the Reagan administration's concerns is the Soviets' testing of a missile known as the PL5. Under past SALT agreements, each side is allowed only one "new" missile. The Soviets previously have said they are testing a new missile, the SSX24. But the Soviets also have made four flight tests of the PL5, and U.S. officials believe it may also be a new missile.

The Soviets claim that the PL5 is a modernized version of their older SS13 version and that its modernization is within the limits allowed by past agreements. U.S. officials believe the missile's warhead and weight differ from those limits by more than is allowed. This is important because it could affect whether the new missile could carry multiple warheads instead of just a single warhead, as does the older SS13.

The U.S. officials are concerned that some old SS16 intercontinental missiles, which were banned by the SALT agreements, may be deployed at a Soviet missile base. The Soviets have denied this.

The Reagan administration also is concerned about a new Soviet radar that may violate the ABM treaty if it is intended to be used to guide anti-missile defensive missiles. The Soviets reportedly claimed that its purpose is to track objects in space.

Other U.S. concerns include claims that the Soviets are encoding the electronic signals sent to the ground during missile-flight tests to a greater extent than allowed in SALT agreements. By monitoring such electronic signals, both sides can have some idea of what kind of missiles each side is testing.

The trade magazine Aviation Week and Space Technology has reported another alleged violation of the ABM treaty involving recent Soviet tests of a technique for rapidly reloading anti-missile interceptor missiles on their launching pads. Each side is not supposed to have extra missiles at such sites.

There appears to be fairly wide agreement among U.S. officials that the Soviets have violated the spirit of SALT agreements. But there is still debate about whether technical violations can be proven. This is due in large part, officials said, to the vague language of the agreements and loopholes in them. Reagan has said that it was difficult to get "hard and fast evidence" of specific violations but that there were "increasingly serious grounds for questioning" whether the Soviets were complying with the agreements.