Washington — Positions seem to be hardening on the question of whether or not to stop America's nuclear arms buildup.
Differences between the Reagan administration and those advocating a ''freeze'' on nuclear weapons production are becoming even more sharply drawn.
Those hoping for some form of compromise on the issue were heartened by President Reagan's call for a meeting with Soviet President Brezhnev to discuss nuclear arms control.
But the ongoing public debate over the issue--which seemed to grow more intense in Washington this week--illustrates the immense practical problems involved in getting competing nations to give up some of their most awesome weapons.
In an address Tuesday at Georgetown University's Center for Strategic and International Studies, US Secretary of State Alexander M. Haig Jr. explained why the administration feels it must continue to build its strategic nuclear forces and refuses to renounce the first use of such weapons.
At the same hour, members of the five-nation US-Europeace Tour were reporting on Capitol Hill the success of their just-completed swing though 52 cities in 37 states. These elected officials, religious leaders, and peace movement organizers pronounced themselves ''very encouraged'' by the response Americans gave them over the past two weeks, highlighted by a candlelight procession of 15 ,000 people in Philadelphia.
While focusing on the planned deployment of Pershing II and ground-launched cruise missiles in Europe, the Europeans (from Britain, Denmark, West Germany, Italy, and the Netherlands) called on the United States and the Soviet Union ''to implement an immediate freeze on production, testing, and deployment of nuclear weapons.''
In this highly symbolic cross-town dialogue, however, Secretary Haig reemphasized the administration position that ''such a freeze would remove all Soviet incentive to engage in meaningful arms control.''
''For the foreseeable future,'' Mr. Haig said, ''The relationship between the United States and the Soviet Union will be one in which our differences outnumber points of convergence.''
As if to reassure the European freeze proponents and their American counterparts, Haig stressed that ''no one has ever advocated nuclear war . . . no responsible voice has ever sought to minimize its horrors.''
At the same time, however, he repeated the policy (agreed upon by NATO in 1967) of a flexible response, which includes the option of launching a nuclear strike in the face of overpowering Soviet conventional forces.
''Flexible response is not premised upon the view that nuclear war can be controlled,'' Haig said.
But a pledge of ''no first use,'' he added, ''leaves the West nothing with which to counterbalance the Soviet conventional advantages and geopolitical position in Europe.''
The complex relationship between strategic nuclear, theater nuclear, and conventional forces was also illustrated in Haig's speech. He noted that the Soviet Union did not agree to negotiate on antiballistic missiles (in the early 1970s) and more recently on ''Euromissiles'' until the US moved to deploy these weapons. Talks in Vienna on reducing conventional forces have been stalled for eight years, however, and the US says this is because of what it calls a vast Soviet advantage.
''It is unrealistic to believe that the Soviet Union will agree to reduce the most threatening element of its force--its heavy, multiheaded intercontinental missiles--unless it is persuaded that otherwise the United States will respond by deploying comparable systems itself,'' Haig said.
Here again, recent action illustrates the administration's problems. The Republican-controlled Senate Armed Services Committee last week refused funds to deploy the new, heavy, multiheaded MX missile. In usually conservative Virginia, elected supervisors in Loudoun County this week joined the growing movement for a nuclear freeze.
Europeace group members will be joined by American freeze supporters for a demonstration at the United Nations Second Special Session on Disarmament in New York when Mr. Reagan speaks there in June.