U.S. and Soviet strategic nuclear weapons are in balance today and can be kept that way "without excessive effort on our part," Defense Secretary Harold Brown said yesterday.

Despite the Soviet buildup over the last 10 years, Brown told the Senate Armed Services Committee, the United States could still absorc "a well-executed Soviet surprise attack" and strike back "with devastating power."

This ability, together with modern U.S. strategic missiles, bombers and submarines now deployed, does not "support the belief that our nuclear capabilities fall short of equivalence with those of the Soviet Union," Brown said.

Brown's relatively calm view of the Soviet threat comes after months of strident warnings from such groups as the American Security Council and the Committee on the Present Danger, and arms specialists like Paul H. Nitze and Air Force Maj. Gen. George Keegan, retired head of Air Force intelligence.

Declaring "we would prefer to see the present stability maintained or enhanced through equitable arms control agreements and at lower force level," Brown assured the committee that "with or without such agreements, the balance can be maintained in the future without excessive effort on our part, providing that we size, select and modernize our forces adequately."

Long-range missiles, bombers and submarines constitute the strategic forces. They take a relatively small slice of the total defense budget, $10.6 billion out of the $120.3 billion President Carter earmarked for the Pentagon in his revision of former President Ford's budget.

Brown said he did not expect the strategic forces to take a "substantially greater" portion of th Pentagon budget in the future but pledged to do "whatever is necessary to keep a stable strategic balance in the years ahead."

The best way to measure the balance of overall military power between the United States and the Soviet Union, Brown said, is to assess how American forces would perform in the most likely contingencies.

Using that kind of measure, rather than counting missiles and other forces on each side, shows that "overall, the balance of power is not at present unfavorable to the United States and its allies," Brown said.

Brown also expressed more skepticism than did one of his predecessors, James R. Schlesinger, about containing nuclear war once the first H-bomb had been used by either the United States or the Soviet Union. Schlesinger had urged that it was conceivable that the superpowers might want to destroy only each other's military targets, not people, in a nuclear war and that therefore U.S. strategic forces should be improved to give the President a "limited nuclear option."

Said Brown yesterday. "In my judgment, any use of nuclear weapons would run the risk of rapid escalation."