The estimated cost of reparations for Japanese-Americans interned during World War II was reported incorrectly yesterday. The correct figure is $3 billion to $4 billion.

A government commission yesterday issued the most detailed accounting yet of the World War II internment of 120,000 West Coast Japanese-Americans, and concluded that it was a "grave injustice" caused by "race prejudice, war hysteria and a failure of political leadership" from President Roosevelt on down.

The exhaustive 467-page report of the Commission on Wartime Relocation and Internment of Civilians is the first phase of a process expected to lead to a recommendation by June that compensation be paid to those who were detained.

It is designed in part to prepare the public and Congress, which set up the commission, for reparations proposals that could cost $3 million or $4 million in payments of up to $20,000 each for the personal suffering and property loss of those removed from the West Coast and confined in relocation camps after the Japanese attack on Pearl Harbor.

The commission also is considering payments to Aleuts evacuated after the Japanese attack on the Aleutians. While the commission did not challenge the need for that evacuation from a war zone, it criticized the "deplorable conditions" in abandoned mines and fish canneries where they were housed in southeastern Alaska. Ten percent of the evacuated Aleuts died during their two- or three-year stay.

After a review of thousands of documents kept secret during the war, the commission concluded that the claims of "military necessity" and disloyalty used to justify the internment had no basis in fact. "Not a single documented act of espionage, sabotage or Fifth Column activity was committed" by a Japanese-American, the study said.

The press and public officials at every level came in for criticism for fueling the hysteria. President Roosevelt, the commission said, approved the evacuation "without raising the question to the level of Cabinet discussion or requiring any careful or thorough review of the situation," despite having information that it was unnecessary.

Roosevelt then prolonged the detention of the Japanese-Americans in the relocation centers in 1944 because he feared negative political reaction in that year's presidential election, the study said. "Whatever the military, legal or moral virtues of the evacuees' cause," it said, the president did not want to "do anything precipitous to upset the West Coast. There would be an election in November."

The average stay for detainees in the camps was 900 days.

"For every citizen and for American public life," the report said, the events of the period "pose haunting questions about our country and its past."

Lt. Gen. John L. DeWitt, the Army official in charge of West Coast security, was criticized particularly for helping the movement to evacuate the Japanese-Americans on the openly expressed theory that "ethnicity determined loyalty."

In a news conference yesterday, commission Chairman Joan Z. Bernstein called the roundup "particularly sobering because men of the greatest stature with careers of the most distinguished public service--Democrat and Republican, conservative and liberal, judges, legislators and Cabinet members, the president himself--were personally involved in a course of action which today we can only find gravely unjust and deeply injurious."

Many of the individual documents and factual findings used by the commission have been previously uncovered by scholars since the war. The report brings them together for the first time and constitutes the first thorough official inquiry.

The report also includes a complete description of conditions in the camps, located in out-of-the-way and generally arid sections of California, Arizona, Idaho, Wyoming, Colorado, Utah and Arkansas. They were short on medical and educational facilities, space and especially privacy, the report said, but amply supplied with armed guards and barbed wire.

Commission members are Rep. Daniel E. Lungren (R-Calif.), former senator Edward W. Brooke (R-Mass.), former representative Robert F. Drinan (D-Mass.), Arthur S. Flemming, former Supreme Court Justice Arthur J. Goldberg, the Rev. Ishmael Gromoff of Alaska, Judge William M. Marutani of the Philadelphia Court of Common Pleas and Washington state Sen. Hugh B. Mitchell.