Interior Secretary James G. Watt publicly apologized to American Indians yesterday in an effort to head off a united call for his ouster by the nation's two largest Indian organizations.

"If my words have caused hurt, I apologize for that hurt," Watt said in a surprise appearance here before a large gathering of tribal leaders, who had denounced him earlier for calling Indian reservations examples of "the failure of socialism."

"But," Watt added, "I don't apologize for the message because the Indian people have been abused by the U.S. government for too many years, and we've got to bring about change."

Watt appeared unannounced at a packed meeting of the National Congress of American Indians, one day after its leaders joined the board of the National Tribal Chairmen's Association in recommending that they draft a statement calling jointly for Watt's ouster.

Watt, who is also the trustee for Indian land and resources, said he wanted to clear up "terrible confusion" over a televised interview in which he said that Indian reservations had fostered poverty and disease, and that some tribal leaders were using the system to enrich themselves while hurting their people's chances to advance.

Those remarks were greeted with anger and confusion in Indian country, where they were widely interpreted as a veiled call for an end to reservations, Indian homelands. But Watt said yesterday that he had intended only to express deep concern for Indian problems and to pledge support for stronger Indian self-government on reservations.

He used the word "socialism," he said, to criticize the federal bureaucracy, which Indian leaders have attacked for years as a hindrance to tribal self-determination.

Watt made no reference, though, to the other major complaint of Indian leaders, the Reagan administration's deep federal budget cuts that have eliminated thousands of jobs on reservations, which generally have no private sector to absorb the layoffs.

"I have drawn the attention of America to some heartfelt problems," Watt said, urging the leaders to capitalize on the national furor about his remarks. "Maybe I used some inartful language, but we got attention."

The surprise apology from the usually combative secretary created a schism between the Indian congress and the powerful tribal chairmen's group over how to respond to Watt's remarks, which Indian leaders said they still considered insulting to Indian culture.

The tribal chairmen's group, representing 154 tribal leaders, voted unanimously in a closed session immediately after Watt's apology to call on President Reagan to fire him for "inaccurate and reckless remarks," which they said distorted the reasons for Indian suffering.

"The manner in which Watt discussed Indian reservations . . . not only reveals his inability to address these problems, but promotes general misunderstanding of the federal Indian trust responsibility," the chairmen said in a letter to Reagan.

Meanwhile, the National Congress of American Indians, whose members include rank-and-file Indians and several Indian organizations, put off voting on the matter until Friday, saying they need to study the question further.

"This is a political question, and we've got to face the reality of it," said Joseph DeLaCruz, president of the congress and chairman of the Quinalt tribe in Washington state.

"There's a lot of merit to us going after him, but if 2 million environmentalists can't remove the man, I don't know what our calling for his resignation is going to do," said Gordon Thayer, chairman of Wisconsin's Lac Courte Oreilles tribal board, which called for Watt's resignation because of the interview and the Reagan administration record on Indian affairs.

Watt's visit apparently tempered the anger of several Indian leaders, who said they admired his candor and his willingness to talk directly with them. His apology was greeted with a loud ovation, although the audience responded with only polite applause when he arrived.

Indian leaders who continued to call for Watt's ouster accused him of a wide assortment of misdeeds. Some said he had failed to live up to treaty obligations to "provide a variety of health, education, and social services to Indian people."

"I'll tell you what people are angry about," said Hollis Stabler, a board member of the Indian congress. "They're angry about the desperate situation they're in, and this has given them a way to strike back."