Two defense leaders gave an unusually optimistic report yesterday on the state of American defenses, stresing that the United States is still No. 1 in the world militarily.

Charles W. Duncan Jr., deputy secretary of defense, and Navy Secretary W. Graham Claytor Jr. spoke to separate Carter administration officials stepped up the campaign to convince the public that signing an arms control agreement with the Soviet Union would be an acceptable risk.

"Despite te momentum of the Soviet buildup," Duncan told the Association of U.S. Army's annual meeting here, "all of us need to recognize a third reality: it is that, where it counts, the worldwide military balance remains favorable to us."

While repeating the oft-stated Pentagon line that one reality is that the Soviets are continuing to build up their military forces and have continued to do so whether U.S. defense budgets go up or down, Duncan said the Soviets are confronted with a number of disadvantages.

One, he said, is that they have had to resort to a "two-contingency strategy" and deploy forces on both the NATO and Chinese fronts.

"The Soviets now station perhaps a quarter of their general-purpose ground and tactical air forces near the borders of China," the deputy defense secretary said. "For now, the Soviets face a more complex and demanding strategic environment than we do."

Soviet forces in the Far East are at the end of a "long and tenuous" supply line, Duncan said, which confronts their navy with serious problems.

"To acquire some elbow room" for their Far East naval forces, he said "the Soviets must try to exercise control over the Barents Sea and Sea of Okhotsk. That isn't cheap. In fact, we would not want to trade geographical places with them."

Duncan added that U.S. NATO allies are much more reliable than Soviet ones in the Warsaw Pact and that national security is not just guns but "a complex mix of strengths - political, industrial, technological, national cohesion and will as well as military strength."

Duncan came close to conceding that U.S. officials had overstated the Soviet military threat in the past, declaring: "In the understandable desire to reverse the antidefense mood and the propensity for reduced defense budgets of the early 1970s, we have tended to present the trends in Soviet military budgets and capabilities independently of the many qualifications I've just listed.

To sum up I see no grounds for believing that today we are any worse off militarily than we were five years ago. We were No. 1 five years ago; we are still No. 1 today."

Claytor, speaking to a Navy League luncheon in Stanford, Conn. also stressed the Soviet geographic disadvantages in declaring that "in spite of all we read about the growth of the Soviet Navy - and it is certainly increasing steadily in capability - we are still No. 1."

Running down the various Soviet fleets and their geographic disgeographic disadvantages, Claytor said, fleets and their geographic disadvantages, Claytor said, "The Soviet Baltic fleet can be bottled up in the event of hositilites by mining the Danish straits. The Soviet Black Sea fleet can be bottled up by mining the Turkish straits. The Soviet Mediterranean squadron would lead an exciting but brief existence in the event of war, and would have no way of getting out of the Mediterranean, the exits to which can easily be mined or blocked by submaries by the West."

Focusing on the ships available to the Soviets' Far Eastern forces, Claytor said "large portions of the Soviet Pacific fleet are based at Vladivostok on the Sea of Japan and can be bottled up by similarly closing the straits leading out of the Pacific."

"The only fleet having a semblance of access to the open oceans is the northern fleet," Claytor continued. "And even that fleet has to travel all the way around Norway and fight its way through the Greenland-Iceland-United Kingdom gap into the Atlantic Ocean," which the United Staes and its allies guard with aircraft and subs.

Claytor said the U.S. Navy still has two big problems in relation to the Soviet navy: fewer ships and more ocean to cover.