Secretary of State Alexander M. Haig Jr. said yesterday that "the heel of the military boot" will not be able to put down popular resistance in Poland, and he forecast growing economic, social and political pressures on Warsaw's martial law regime.

Among the most serious of the pressures, Haig indicated in an interview on CBS Television, would be "the total collapse of an already stuttering Polish economy." This is likely to become increasingly evident in the days and weeks ahead, he said.

The United States, as President Reagan disclosed in an address to the nation Wednesday night, is seeking to use its leverage and that of its allies to encourage a change in direction by Gen. Wojciech Jaruzelski. Reagan said he had informed Jaruzelski by letter of "serious consequences if the Polish government continues to use violence against its populace," and that he appealed to the Polish leader to free prisoners, lift martial law and restore free speech and association.

Asked if it is realistic to expect that the crackdown can be reversed at this stage, Haig replied:

"I don't think we're talking about rollback. We're talking about the continuation of a situation in Poland in which the church, the Solidarity and the government work together to rejuvenate, if you will, or reinstitute the reforms that have progressed over the last 18 months."

Haig said he did not anticipate Solidarity would be reinstituted as it existed in the final days before the crackdown. But a liberalization process involving the majority of Poles is "inevitable," the secretary of state said, despite "whatever repression is applied."

Regarding relations with the Soviet Union, Haig said that a warning letter had been sent by Reagan to Soviet President Leonid Brezhnev because in a relationship this vital "it is important that we clearly lay out precisely what we expect" in advance of taking actions.

Haig, asked about the scheduled resumption Jan. 12 of Soviet-American negotiations on limiting nuclear arms in Europe, said, "We intend to go back" to the bargaining table.

He added, however, that a "very careful" assessment of Soviet actions will continue in the meantime. Haig did not say how long Reagan is willing to wait before taking the "concrete political and economic measures" against the Soviets that he promised Wednesday night "if this repression continues."

Haig said Reagan has "a great sense of urgency" about a return to moderation in Poland. "If that does not occur, I can assure you that the president is prepared to deal with that," the secretary of state declared.

State Department spokesman Dean Fischer told reporters at midday that no official Polish or Soviet reaction to the president's speech had been received. Fischer rejected an unofficial reaction by Tass, the Soviet news agency, which accused Reagan of interference in Poland's internal affairs.

Haig, in his television interview, said the United States is not interfering in internal affairs because "the Soviet Union, Poland and the United States are signatories to the Final Act of the Helsinki accords" and as such "we have an obligation to point out unequivocally when violations of those understandings occur."

The Helsinki accords, signed in 1975, commit the signatories, among other things, to respect human rights and fundamental freedoms. They established procedures for following up on this and other commitments.

Fischer reported that there is "increasingly broad and stinging world criticism" of the martial law regime, but that Polish media are seeking to deflect this by portraying current conditions as "returning to normal."

Stanislaw Pawliszewski, the minister-counselor of the Polish embassy here, who took charge after the ambassador, Romuald Spasowski, took political asylum in the United States, told reporters at the State Department yesterday that strikes are decreasing and calm is returning to Poland. The U.S. position is that the situation is not improving, Fischer said in response.

Pawliszewski was summoned to the State Department to discuss implementation of the retaliatory measures regarding Poland that Reagan announced Wednesday night.

The State Department officer who met the Polish envoy yesterday wore a Solidarity lapel button.

The silver-haired Pawliszewski, asked by reporters if he too is thinking of seeking asylum in the United States, replied tersely, "I am not."