The Western European allies believe that the SALT II limits on nuclear weapons should not be allowed to lapse, and fear that a U.S. decision against continued observance of the accord would be a setback for arms control, according to a number of allied government officials interviewed recently.

Several North Atlantic Treaty Organization governments, as well as NATO Secretary General Lord Carrington, have let the Reagan administration know that refusal to respect SALT II now could generate a hostile public backlash.

One European political leader, reflecting a widespread view, said that doing away with SALT II would make it more difficult in general for allied governments to defend the idea that the Reagan administration is sincere about arms control.

The Europeans say they are acutely conscious of their reputation in some U.S. circles as weak-willed, interfering partners. They say they have remained discreet in expressing to Washington their desire that the United States not break the treaty restrictions when they expire at the end of this year.

But they nevertheless have followed closely internal administration debates over continued U.S. observance. Officials said that the U.S.-Soviet treaty, which never was ratified by Congress but to which both countries pledged adherence until expiration, will be a key topic in their discussions with Secretary of State George P. Shultz when NATO foreign ministers meet in Estoril, Portugal, this week.

Already, Dutch Foreign Minister Hans van den Broeck is said to have told Shultz that breaking out of SALT II limits would make it even more difficult for his government to win public support for deployment of 48 cruise missiles this fall.

"There will be many, many discussions between now and the 10th" of June, when the administration is due to inform Congress of its SALT II plans, one British official said.

Shultz is said to share the European belief that although the Soviets may have "cheated" on compliance, SALT II should continue in some form.

Shultz is expected to use the European warnings as ammunition in the debate with Defense Secretary Caspar W. Weinberger, who is said to argue that the treaty has been "unsuccessful" in holding back the Soviets and should be abandoned.

But while they continue to hold discussions with U.S. officials, the allies say they are reluctant to press the administration, or to make their views public. To do so, officials here and in West Germany said, would give the impression of a possible rift between them and the United States just as the second round of U.S.-Soviet talks on nuclear weapons reductions are to begin in Geneva.

At the same time, European governments feel that they have spent a significant amount of alliance capital recently in wavering over deployment of medium-range missiles, questioning U.S. economic policies and in their somewhat equivocal response to President Reagan's Strategic Defense Initiative.

Since SALT II is a bilateral accord between the United States and the Soviets, the British official said, it would be seen as "a bit cheeky to tell the U.S. what to do."

This official and others in the government and private defense community here said that the British government has three criteria on which its concerns about the SALT II decision are based.

First is that it "not undermine the whole process of arms control," either substantively or by supporting public notions here that Reagan is not serious about the subject.

"There is no public relations value in terminating the treaty," one defense academic said. "Now that the Russians have said they are willing to carry on" with the treaty from their end, "for the Americans to say no would be very silly. It is hard to see what they would gain."

Arguments by U.S. officials such as Assistant Defense Secretary Richard Perle that the Soviets already are so far ahead of the United States in ballistic missiles that the treaty is meaningless "have no intellectual substance," he said. "If the numbers don't matter, why are U.S. officials always putting out all those charts and graphs, and talking about gaps?"

The second British concern, officials here said, is that "whatever is decided helps in Geneva."

"The European view, or at least the British view," said one official, "is that we are basically in favor of arms control. Anything that makes that more difficult, or undermines existing agreements, we're against."

Thirdly, they said, there is an inherent element of "alliance management" in the SALT II decision, and a need to allay allied concerns even if consultation is not mandatory.

Several European allies remain skeptical about administration claims that it has the right to "break out" of arms control deals because of Soviet violations.

There is some concern about the Soviet encoding of missile test data and deployment of SSX24 missiles that are expected to become operational next year. But the Europeans say such matters are not grave enough to warrant desertion of the SALT II framework.

In addition, there is some disagreement between Washington and the allies over what the administration has described as a principal example of Soviet treaty violations.

The view of many in the Pentagon is that the Soviet radar installation at Krasnoyarsk in Siberia is a battle-management facility that violates the antiballistic missile treaty.

The Europeans say they have not seen satellite reconnaisance photos that lead them to believe that the radar system is anything but an early warning or space tracking station. "We don't absolutely think it is a violation," an official here said.

The Europeans say, however, that they will continue to be discreet in expressing their concerns. "There is a limit to how much Europe can get involved in American strategic planning," said the academic.