President Reagan challenged the Soviet Union yesterday to put aside rhetoric and join in "a serious, practical approach" to reducing tensions in Europe through negotiations.

Reagan issued the challenge in a written statement following a White House meeting with James E. Goodby, the chief U.S. negotiator at the year-old East-West conference on Confidence and Security-Building Measures and Disarmament in Europe, known as CDE.

This East-West forum, an outgrowth of the earlier Helsinki accords, seeks to improve and extend arrangements for advance notification of military exercises and other measures that could ease fears of military clashes between the two blocs in Europe.

Goodby and his delegation will meet representatives of the Soviets and 33 other nations in a fifth round of talks in Stockholm on Jan. 29.

In what has been described as a procedural breakthrough, the Soviets agreed last month to formation of CDE working groups that the United States hopes will shift the focus in Stockholm from rhetoric to specific proposals for confidence-building measures, most of which originate with the West.

With creation of these working groups, Goodby said in an interview, the conference is entering "the intense discussion phase" that could center on negotiable proposals.

"We will have to see within the next year if the Soviets are going to get down to business," Goodby said.

Reagan recalled that, prior to the opening of the negotiations a year ago, he sought "to meet the Soviets' concerns in Stockholm halfway" by agreeing to discuss the principle of renunciation of the use of force "if this would lead them to negotiate seriously on concrete measures to give effect to that principle."

The president added, "The Soviet response to our invitation to negotiate has not been forthcoming. The Soviets have yet to demonstrate any willingness to put aside those ideas which are more rhetorical than substantive; they have yet to join the majority of participants who favor a serious, practical approach to develop meaningful confidence-building measures."

Reagan said the Stockholm negotiations, which primarily concern nonnuclear forces, complement the three-part nuclear-oriented negotiations that Washington and Moscow are expected to begin soon as a result of last week's meeting of Secretary of State George P. Shultz and Soviet Foreign Minister Andrei A. Gromyko.

"Complementing those arms control efforts which seek to reduce force levels, the Stockholm conference addresses the proximate causes of war -- miscalculation and misinterpretation -- and seeks to ensure that those forces are never used," Reagan said.

Meanwhile, a spokesman for Secretary of Defense Caspar W. Weinberger denied that he is linking the administration's Star Wars anti-missile plan with a buildup of conventional air defenses.

The New York Times quoted Weinberger as saying that the Star Wars plan, if deployed, would have to be backed up by anti-aircraft radar installations and planes to protect North America against bombers. Former secretary of defense James R. Schlesinger was quoted as saying such a system would cost at least $50 billion yearly.

Pentagon spokesman Michael I. Burch said "there's no connection" between the anti-missile and anti-aircraft programs.