President Reagan said yesterday the United States is continuing to conduct research and testing of the "Star Wars" antimissile defense system "within the terms" of the 1972 Anti-Ballistic Missile Treaty, but other U.S. officials said it remains unclear, after weeks of controversy, how those terms will be interpreted by the administration in the future.

Reagan devoted his weekly radio address to an appeal for public support of his Strategic Defense Initiative, also known as the Star Wars program, and to a demand that the Soviet Union "come clean" on its strategic defensive programs.

Reagan charged that Moscow is engaging in "dangerous deception" by pretending it has no such program while as many as 10,000 Soviet scientists and engineers are thought to be working on "research related to SDI."

The president spoke, as he has on several recent occasions, of "research" and "testing" as elements of the U.S. space defense project, which he previously has described as being conducted in accordance with the ABM Treaty.

Research of all sorts is permitted under the ABM Treaty signed with the Soviets during the Nixon administration, but "testing, development and deployment" of space-based, sea-based, air-based or mobile land-based ABMs are prohibited.

Until a week ago, the Reagan administration's justification for certain planned tests of Star Wars was that these were too rudimentary or peripheral to be the kind of "testing" barred by the ABM Treaty.

However, a statement last Sunday by White House national security affairs adviser Robert C. McFarlane opened the way to a new interpretation of the ABM Treaty that would allow virtually unlimited "testing" and "development" of Star Wars.

The adverse reaction last week from U.S. allies and members of Congress to McFarlane's reinterpretation of the 13-year-old treaty has generated serious concern in some administration circles and led to new high-level consideration of what the future administration position should be, according to official sources.

One proposal reported under consideration is to reaffirm U.S. commitments to live within the ABM Treaty as previously interpreted by the administration, even while saying this is not strictly required by a new analysis of the 1969-1972 ABM negotiations.

Senior arms control adviser Paul H. Nitze was questioned sharply about the revised administration view of the ABM Treaty in Europe last week, where he had gone to brief NATO officials on the recent Soviet arms offer and preparations for next month's summit meeting of Reagan and Soviet leader Mikhail Gorbachev.

Lt. Gen. James A. Abrahamson, director of the SDI program, was peppered with similar questions during an appearance Friday in San Francisco before the North Atlantic Assembly, legislators of the NATO countries.

Secretary of State George P. Shultz is expected to face similar questions in an appearance before the legislators in San Francisco Monday and in a meeting with NATO foreign ministers in Brussels Tuesday.

As of yesterday, officials were uncertain what Shultz would say. They reported that alternative drafts of his remarks were circulating in the administration.

Rep. Dante B. Fascell (D-Fla.), chairman of the House Foreign Affairs Committee, on Wednesday called the administration's new interpretation of the ABM Treaty "incredible."

Fascell also announced that he would hold hearings on the issue.

Rep. Norman D. Hicks (D-Wash.) said Friday he will seek to amend the defense appropriation bill now before Congress to require the Star Wars program to abide by the previous U.S. interpretation of the ABM Treaty.

Legislation requiring ABM Treaty compliance has passed Congress overwhelmingly in the past two years.

Statements made in 1972 by the U.S. negotiators of the treaty and repeated in various ways by the Nixon, Ford, Carter and Reagan administrations since then said that "testing" and "development" of future anti-ballistic systems based on lasers, directed-energy weapons and other exotic space-based technology is limited by the ABM Treaty.

However, a legal review of the negotiating record carried out in the Pentagon earlier this fall -- and endorsed by State Department legal adviser Abraham D. Sofaer -- concluded that the previous U.S. declarations had overstated what had been decided in the ABM negotiations.

This review concluded, according to administration officials, that the Soviet negotiators did not accept limits on "testing" and "development" of exotic space-based systems, although it had been a U.S. objective at the time to persuade them to do so.

Reflecting this view, McFarlane said last Sunday on "Meet the Press" that "testing" and "development" as well as research "involving new physical concepts . . . are approved and authorized by the treaty."

Two days later, a senior White House official said at a "background" news briefing that McFarlane's statements reflect a new and fixed position of the administration.

Retired ambassador Gerard Smith, who was chief U.S. negotiator of the ABM Treaty, said in a news conference Friday that under the McFarlane position "we in effect will be harpooning the whole ABM Treaty just about six weeks before we go into a summit meeting, and directly after having received a new Soviet proposal on arms control."

Smith said the new position "makes a dead letter" of the 13-year-old treaty.

Smith and the legal counsel to the ABM delegation, John B. Rhinelander, ridiculed the idea that the Soviets did not accept a ban on testing and development of exotic systems.

This position is "saying in effect that we're not sure the Soviets knew what they were signing," Smith declared.

Reagan, in his radio address, charged the Soviets with "an out-and-out violation" of the ABM Treaty in constructing a large phased-array radar in central Siberia.

He said the Soviets are engaged in "a number of activities that raise questions about their commitment" to the 1972 Treaty.

In appealing for support of the SDI program, Reagan said it was intended to create "a balance of safety" in the world through defense against incoming missiles, thus replacing the "balance of terror."