NATO endorses Reagan plan for US-Soviet nuclear arms reduction

President Reagan's call for US-Soviet strategic arms control talks next month , with the aim of reducing stockpiles of nuclear warheads by a third, has been greeted warmly at the NATO foreign ministers' meeting here.

At the end of their two-day spring meeting, the foreign ministers called the Reagan proposal ''a far-reaching but realistic offer that would . . . strengthen peace and international security.''

NATO Secretary-General Joseph Luns said that the NATO allies were ''extremely happy'' with the American initiative.

At the same time, Mr. Haig was especially critical of Soviet President Leonid Brezhnev's offer of a nuclear freeze -- an idea that has been proposed by the Soviets in one form or another for some time.

The US goal, Haig said, has always been a ''significant reduction to equal levels.'' A freeze is simply ''not sound arms control,'' he said, because it would result in equal levels as a starting point for negotiations.

The US has claimed that such an approach would only serve to prolong present Soviet superiority in the nuclear field.

Haig did warmly welcome Brezhnev's encouraging words on negotiations aimed at an eventual reduction in nuclear arms. ''That, we welcome,'' he said. ''It coincides with our position.''

Brezhnev's reference to the need to respect the security needs of both superpowers was also -- not unexpectedly -- given the US secretary of state's initial stamp of approval.

''Clearly,'' Haig said, ''that's not incompatible with a balanced approach to arms control.''

Haig's qualified approval of the Brezhnev response to President Reagan's proposal is being seen by European officials as perhaps a significant opening step on the path to serious negotiations on the question, which Reagan suggested could begin by the end of June.

Most governments in Western Europe have come under increasing pressure from a swelling antinuclear peace movement to press the two superpowers to halt the arms race and begin sincere talks aimed at reducing arms levels -- particularly nuclear weapons.

But there was no mention whatsoever at the spring meeting of NATO foreign ministers this week of a reversal of the decades-old NATO policy of deterrence.

''Deterrence has kept the peace in Europe for over 30 years,'' the NATO communique released after the meeting said, ''and this policy is still valid today.''

Soviet policies, in fact, confirm the need for the allies to make ''all necessary efforts to maintain a strong and credible defense,'' the communique said.

Preserving the peace, the NATO communique said, ''requires a wide range of conventional and nuclear forces designed to persuade any potential aggressor that an attack would be repulsed and would expose him to risks out of all proportion to any advantage he might hope to gain.''