President Reagan has drafted a formal statement committing himself to improving the lot of American Indians, the nation's most impoverished minority group and one that has been particularly hard-hit by his budget cuts in federal programs for the poor.

An outline of the long-awaited statement, released over the weekend, was denounced yesterday as an empty gesture by a range of Indian leaders, who blamed Reagan's fiscal policies for unemployment rates of up to 90 percent on reservations. The full statement was expected to be made public later this week,

"The words sound lovely, but the real Indian policy of this administration was set in the first budget the president sent to Congress, which proposed to cut one-third of the total budget for Indians," said Suzan Harjo of the Native American Rights Fund, which represents Indian tribes before Congress and the courts.

The policy reasserts the commitment of past administrations to Indian self-determination, and proposes to address the Indians' economic plight by promoting free enterprise on reservations and enforcing new laws aimed at strengthening tribal governments.

In an accompanying executive order, Reagan created an advisory presidential commission to identify obstacles to private business on reservations and to suggest ways to reduce tribal dependence on federal funds.

"Excessive regulations and self-perpetuating bureaucracy have stifled tribal decision-making, thwarted Indian control of reservation resources and promoted dependency rather than self-sufficiency," the White House said in a "fact sheet" on the policy. Administration officials portrayed the policy as a sequel to the forceful Indian self-determination statements of President Nixon and Congress in the 1970s.

But Indian leaders said the Reagan policy falls short of its precursors, and charged that federal budget cuts have made it impossible for the federal government to meet its obligation as trustee for Indians.

This obligation, stated in treaties and laws, requires the United States to ensure Indian health and welfare and the proper development of natural resources in return for the millions of acres of Indian land ceded by the tribes to the federal government.

"The activities of the last two years speak louder than any rhetoric," said Elmer Savilla, former chairman of the Quechan tribe of California and now executive director of the National Tribal Chairmen's Association. "Indian tribes feel they've lost almost three-quarters of what they had two years ago."

Recent budget cuts in programs for the poor, such as welfare, food stamps and job training, have hit Indians disproportionately because they have the lowest per capita income of any group in the country. Indians also have the worst health and housing conditions, the lowest educational levels and the highest suicide rate in the United States, according to a report prepared by the Carter administration.

"If you've been around Washington as long as I have, you're not optimistic that an advisory commission is going to do much about these problems," said Forrest Gerard, assistant interior secretary for Indian affairs in the Carter administration and a member of Montana's Black Feet tribe. "It takes more than rhetoric. It takes money."

The Indian leaders said they welcomed certain new proposals in the policy statement, such as a White House plan to deal with tribes through the Office of Intergovernmental Affairs, the liaison for states and cities, instead of through the office that works with interest groups such as veterans, businessmen and religious leaders.