Alexander M. Haig Jr., in his second day of testimony on his nomination to be secretary of state, called yesterday for a "rather dramatic improvement" in U.S. military power before resumption of arms control negotiations with the Soviet Union.

Haig's remarks strongly suggested a substantial delay in any U.S. effort to resume negotiations with the Russians on limiting strategic nuclear weapons. Two strategic arms limitations treaties, SALT I negotiated and ratified under President Nixon, and SALT II, negotiated by President Carter but never ratified, have been the focal points of the relations between the nuclear superpowers over most of the last decade.

In some two hours of interrogation by the Senate Foreign Relations Committee, Haig cast new light on a variety of topics, from Cuba to Angola to China, which bear on what he is likely to recommend as the most powerful foreign policy figure in the top rank of the administration of Ronald Reagan.

The senators accepted most of what he had to say in a deferential fashion reflecting a common expectation that, after further days of questioning and attempts to inspect Nixon White House tape recordings, Haig will be confirmed as secretary of state.

The timing and strategy of arms control negotiations with the Soviets is particularly important because a number of provisions of the SALT II treaty will expire at the end of this year. While never ratified by the Senate, the provisions of the treaty have so far been observed by both parties, according to the State Department.

Reagan, in the final days of the presidential campaign, said that "as president, I will immediately open negotiations on a SALT III treaty." Reagan has not repeated the pledge since the election, however.

Last Tuesday, Reagan's choice for secretary of defense, Caspar W. Weinberger, said it would take at least "a good six months" for the new administration to be ready to resume arms control negotiations. On Friday, Haig told the Senate Foreign Relations Committee that this represented a "personal" observation by Weinberger, and that the question of how and when to proceed with the Soviets would be a matter for priority policy-making early in the new administration.

In yesterday's testimony, Haig did not commit himself on precise dates, but his emphatic statements on the preconditions for negotiations seemed clearly to indicate his line of thinking.

"I think we are totally ill-prepared, under the current menu of decisions that have been made [by the Carter administration] to negotiate successfully the kinds of arms control breakthroughs I would like to see," the retired general said. "I would like to have some rather dramatic improvement in our overall posture as an incentive to greater breakthroughs," he added.

Haig's thinking appeared to be a refined version of Reagan's campaign call for the United States to use the "trump card" of a U.S. military buildup to impress the Soviets to make concessions.

While seeming to stave off negotiations on arms limitation, Haig volunteered that he would "not at all" preclude "talks" with the Russians before the U.S. military posture is remedied. But he also said that "we've got to change the backdrop [evidently referring to military power] under which those talks and ultimately the negotiations themselves will be conducted successfully."

As in the six-hour session on his nomination Friday, members of the Foreign Relations Committee broached a great variety of topics to Haig in an attempt to learn his views and exert their influence on them. And as on Friday, Haig in a sometimes gravelly voice, sitting alone at the long witness table, refused to be pinned down to commitments and details.

His answers, even so, were suggestive of attitudes and avenues in the high policy councils of the Reagan administration. Among others, he addressed these topics:

U.S. relations with Cuba, which are likely to be strained in the new administration. Aksed if he would try to improve relations with Havana, Haig replied, with an increasingly hard edge to his voice, "It would be very, very difficult for me to support efforts toward normalization with Cuba so long as they are spawning, instigating, training and conducting terrorist activities in this hemisphere designed to change by force legitimate governments."

The Clark amendment prohibiting U.S. covert or overt operations in Angola, a provision of law that Haig described as "a self-defeating and unnecessary restriction" on the executive branch in a situation that is "highly dynamic."

Cuban troops in Angola tipped the scales of civil war to the current governing group. Haig noted that an opposition group once supported by the CIA, UNITA, is "still virulent and strong, and functioning." Before his election as president, Reagan has suggested at times that the United States should supply arms to UNITA as a counter to Cuban and Soviet efforts.

U.S. relations with the People's Republic of China, which is "a strategic relationship" of overlapping interests that should be further developed but not, however, to function as a constant "irritant" to improved relations with the Soviet Union. Haig did not rule out future arms sales to China, saying that this "extremely sensitive" issue will continue to be reviewed "in the light of the international environment."

Haig declined to give his views on the possible official relations with Taiwan, an idea broached by Reagan last September that caused an explosive reaction in Peking. The secretary of state-designate said he wants to talk at length to Reagan before taking a stand. Haig did say that China has "a long way to go" before it is a military threat to Taiwan.

In discussing U.S. assistance to international financial institutions such as the World Bank, Haig noted that his position was made "extremely delicate" by some campaign statements and provisions of the Republican national platform. The GOP called for emphasis on bilateral assistance -- rather than multinational banks -- whenever possible, and Haig spoke approvingly of the bilateral route.

Responding to a question, Haig rejected any suggestion that he will strictly adhere to provisions of the GOP platform, which he had no part in drafting, though he promised to be aware of them and take them into consideration as decisions are made.

Regarding the use of American power in foreign lands, Haig once again suggested that he would not rule out covert intelligence or paramilitary operations so long as they were reported to congressional committees in compliance with the law. Under persistent questioning by Rep. Paul E. Tsongas (D-Mass.), Haig would not condemn secret U.S. operations in Chile in 1970, when Haig was a White House official, but said they must be understood in the context of U.S. requirements at the time.

Haig expressed a greater degree of hesitancy in the application of open military power by the United States. While disapproving of "a great trending toward abhorrance of anything military" in the wake of the Vietnam war, Haig also said that any use of U.S. military force abroad would be "a profound step."

"It is awfully important that Americans know and recognize that once a drop of American blood is shed in a foreign turf in conflict, that unleashes a chain of actions and counteractions." He said the nation must be prepared to face the growing consequences of battle abroad before taking the first step. t