Defense Secretary Harold Brown said here last night that a simple assertion by the Soviet Union that it would also refrain from producing neutron weapons would be "an unsatisfactory response" to President Carter's decision to defer production of those weapons for allied arsenals.

Brown, speaking at a press conference here after meetings with West German Chancellor Helmut Schmidt and Defense Minister Hans Apel, made it clear that the eventual American decision rested on Soviet willingness to restrict weapons that threaten Western Europe, such as large numbers of tanks or medium-range unclear-tipped SS-20 missiles.

Carter last week decided to defer a decision on whether to produce neutron weapons and said his final decision will depend upon Soviet attitudes toward limiting their arms.

The neutron weapons, which can be fitted on artillery shells or short-range battlefield missiles, are intended as a potential allied defense against numerically superior Soviet tank armies.

But Brown pointed out that the Soviets face no such tank threat from the West and therefore a Soviet offer to merely match the U.S. decision would be insufficient.

Brown also seemed to suggest that Soviet restraint on the SS-20 missiles - which can hit any target in Europe from bases in the Soviet Union - is what the Carter administration seeks rather than just reductions in tank deployments.

Brown arrived here yesterday in the aftermath of the latest flare-up between Bonn and Washington over decisions made by the Carter administration. The latest unpopular move here involved not as much Carter's decision to defer production of the neutron weapons but his last-minute change of course after Schmidt had moved closer to publicly endorsing there politically controversial arms.

The White House action increased concern here and elsewhere in Europe about Carter's alleged unpredictability. There had also been concern expressed over a series of U.S. defense dicisions including the scrapping of the B1 bomber, scaling down of the navy and the neutron decision.

Under questioning, however, Brown said he heard no expression today about lack of confidence in American weapons decisions nor concern that U.S. decision-making was not providing adequate defense.

Under questioning, Brown also said his discussions here were certainly designed "to assure" his west German counterparts that American decisions are made with the intent, "and we believe the effect," of assuring not just U.S. but alliance security.

Brown is one of the more respected members of the Carter administrations here and sources privy to the Schmidt-Brown discussions say the chancellor - if he continued to have uneasy feelings about the White House - seemed to go out of his way to make sure relations with Brown and the U.S. defense establishment were friendly.

The talks with Apel centered chiefly on the question of whether West Germany would support U.S. efforts to have the NATO alliance build a multibillion dollar fleet of airborne warning and control planes - meant to provide surveilliance and early warning of attack over a European battle-field.

Apel said that in principle he supported such a plan but made it clear that Bonn was expecting the United States to buy some West German equipment as an offset to what the Bonn believes will be about a $750 million contribution from them for the planes.

The Brown visit also took place against the backdrop of a five-hour debate in the Bonn Parliament over the neutron weapon.

Schmidt made it clear that while it was solely the decision of the U.S. president whether to produce such weapons, Bonn would accept their stating on West German soil on three conditions.

One is that the decision to deploy them be made jointly by the Western alliance. Two is that efforts be made to negotiate the weapon out of existence in arms control talks with the Soviets. Three is that West Germany not be the only country where the weapons are deployed.

Schmidt had made those points privately to the White House, he claims, beginning in January.

In Parliament, the leader of the opposition Christian Democrats, Helmut Kohl, attacked Schmidt's declaration as both inadequate and too late.

"If Herr Schmidt had shown more courage." Kohl charged, "President Carter's decision would have been easier."

The dedate ended with a vote of 240 to 224 in favor of a pro-government resolution to bring the neutron weapon into disarmament talks and to defer, in the meantime, the decision to produce or deploy it.