Washington — With two important audiences in mind, the Reagan administration has strongly repeated its pledge to increase substantially the ability to deter and - if necessary - to wage war.
In a press conference Thursday, Defense Secretary Caspar W. Weinberger reacted sharply to Soviet President Leonid Brezhnev's tough speech this week outlining moves to increase in size and effectiveness his country's military might.
In essence, Mr. Weinberger said this proves that the current US leadership is correct in pushing for a steady buildup of both nuclear and conventional forces as a means of deterring the Soviet Union from aggression.
At the same time, the US Pentagon chief also addressed the growing number of Americans pushing for a nuclear freeze.
Voters in nine states will decide on nuclear freeze referendums next week, and pastoral letters supporting a halt on the production and deployment of nuclear weapons have been drafted by the National Conference of Catholic Bishops , as well as leaders of Lutheran, Episcopal, and other groups.
''A nuclear freeze would weaken the deterrent forces we rely on to prevent war,'' Weinberger told reporters at the Pentagon. ''A freeze would also make it far more difficult to negotiate substantial nuclear arms reductions with the Soviet Union.''
There have been recent signs that the consensus supporting President Reagan's views on national defense may be waning. Millions of Americans (a majority, according to some polls) favor a mutual and verifiable freeze on nuclear weapons. Business leaders and many Republicans have joined the call for defense cuts in order to improve the domestic economy. There is a growing sense in Washington that it will be increasingly difficult for the administration to carry out its five-year, $1.6 trillion rearmament effort.
But Weinberger said that in order to meet an increasing Soviet threat, military spending will require ''a substantial amount of our resources for a number of years.''
The two nuclear superpowers thus seem to be mirroring each other in warnings about a heightened arms race. The US says it must boost its military might because of recent Soviet advances in strategic and conventional capabilities. Mr. Brezhnev says he must counter the Reagan administration's ''unprecedented'' arms buildup.
Many Americans find solace in the freeze movement, attractive in part because of its simplicity. But administration officials point out that the USSR (unlike the United States) has never agreed to tough verification measures, including on-site inspection.
A freeze, Weinberger said, would increase the danger of war because the Soviet Union has done much more than the United States to modernize its strategic and tactical nuclear forces in recent years. For example, he noted, ''over three-quarters of US warheads are carried on launchers 15 years of age or older, while three-quarters of Soviet warheads are carried by launchers five years old or less.''
But critics point out that the US is in a stronger position since most of its warheads are deployed on relatively invulnerable submarines while most Soviet missiles are ground based and thus more vulnerable.
''We think the passage of the freeze would . . . be something that would encourage the Soviets to stay away from the negotiating table and do all of the things that Mr. Brezhnev said they would do,'' Weinberger said.