The U.S. government has allocated two large, vacant brick buildings 400 yards southeast of the Washington Monument and adjacent to the national Mall for a $30- to $40-million Holocaust museum, federal officials confirmed yesterday.

The decision to place the memorial museum--in memory of Jewish and other Holocaust victims--so prominently, plus its large scale and the official status conferred by its congressional mandate, represent an extraordinary American commitment to remember one of history's darkest periods. The only other memorial on this scale is Israel's Yad Vashem in Jerusalem.

"My hope is that whoever will enter this museum will leave it a different person," said Elie Wiesel, chairman of the U.S. Holocaust Memorial Council, an independent federal agency set up by Congress in 1980 to raise private funds to create the memorial museum.

"Our hope is to create a living museum, not stones, but experiences, memorials, ideas, to keep the past alive . . . for the sake of future generations." Completion is scheduled for mid-1987.

Wiesel, a survivor of Auschwitz and Buchenwald and now a Boston University professor, said transfer of the buildings to the Holocaust council will be announced officially--perhaps by President Reagan--during the Days of Remembrance of the Holocaust, April 10 through 17. Nearly 20,000 concentration camp survivors are expected to meet then in Washington.

Wiesel said the council will announce a $75 million national fund drive for construction and the museum's programs. The council has an $820,000 federally funded budget this year, and has asked for $1,953,000 next year, but Wiesel said he hoped in the future "we don't need the taxpayers' money."

The 138 percent budget increase for next year is needed to pay the sharply increasing number of design, engineering, audio-visual, computer and other consultants required to plan the museum, according to Micah H. Naftalin, the council's senior deputy director. "We've now gone critical with the planning," he said. "It's a major undertaking."

Council officials are negotiating to get a third, smaller building adjacent to the two they have, a General Services Administration spokesman said yesterday.

Council Vice Chairman Mark Talisman said building the memorial museum is "a hell of a challenge. It's going to take every American to get involved . . . It will be an enormous place of learning, of caring . . . It's a museum and memorial to 6 million Jews and millions of others who died . . . Does one call it a Jewish memorial? No, not by any means. The dimensions will be much broader than that."

Among those designated for persecution and death by the Nazis were gypsies, Slavs, Jehovah's Witnesses, homosexuals, political opponents and others. Talisman added that the Holocaust and any related memorial must always have a special meaning for Jews--an entire race targeted for extinction by the Nazis.

Naftalin said, "It's by no means an ethnic or Jewish museum. It's for the whole American people. There will be an emphasis on the role of the liberators" and exhibits noting groups other than Jews who died in the camps.

The Sept. 29, 1979, report by the Commission on the Holocaust appointed by President Carter--which recommended building a memorial museum in Washington--said "special emphasis would also be placed on the American aspect of the Holocaust--the absence of American response (exclusion of refugees, denials of the Holocaust etc.), the American liberation of the camps, the reception of the survivors after 1945, the lives rebuilt in this country and their contribution to American society . . ."

Wiesel chaired the commission, as well as the council that Congress and the Reagan administration later created to implement commission recommendations.

Planning for the memorial museum is still in its early stages, but officials said it would include exhibits to evoke the horror of the Holocaust, an education program aimed at youth, scholarly programs linked with universities around the world and possibly an advanced computer setup to store documents and the names of Holocaust victims.

Extensive consideration is being given by the 65-member council--which includes Jewish leaders, members of Congress and others--to such delicate questions as how children can be exposed to the terrible material in the museum without being traumatized--or even if this is possible.

The two buildings were transferred by the GSA to the council through the Interior Department, the council's parent agency, according to a GSA spokesman. Both Interior Secretary James Watt and GSA Administrator Gerald P. Carmen attended the council's last meeting in December at the Kennedy Center, where Carmen was given an award by the council for his help.

"From evil and from disaster and from all those type of things, good things do come," Carmen responded, according to a transcript. "And if I can just be a non-government official and just be a Jew for a moment, I think that those years that we were growing up in America during the Holocaust and that trauma that we all went through did a lot for us to help us very personally know how much democracy means and how much freedom means." He said the memorial will "be held as a symbol of what can happen when we let down our guard."

According to the same transcript, Watt said the memorial "must be much more than a tribute to the dead. It must be a reminder to the living of the horrors which can be inflicted when tyrannical powers are allowed to gain the military, economic and strategic advantage to do as they will without fear of retribution."

The two buildings are known as annex one and two of the old auditor's complex stretching from 14th to 15th Street along Independence Avenue NW. Council officials said engineering studies of the buildings' structural soundness are under way, but it will be another year before an architect is chosen.

The turn-of-the-century buildings, with 32,000 square feet of space, are long, rambling, two-story red brick structures with a varied history. When they were built, they served as stables and laundry buildings, and at one time or another were used by the Agriculture Department, the Bureau of Engraving and Printing, Bureau of Hatcheries and other agencies. Many of the windows are broken, and much of the inside space is dusty and dirty, but from the 15th Street side of the complex there are sweeping views of the Jefferson Memorial, the Tidal Basin and the Washington Monument.

Distinguishing features are the picturesque roof line, towers, small cupolas and clerestory.

Rep. Sidney Yates (D-Ill.), a council member who helped push the memorial legislation through Congress, recalled how affected the council members were by the buildings when they first saw them. "It reminded some of the members who had just returned from the death camps in Europe of the shape of the buildings in Auschwitz," Yates said. "It had that same overall general shape."

The council's museum-planning team is headed by Rabbi Seymour Siegel of the Jewish Theological Seminary, and includes Anna Cohn, past director of the B'nai B'rith museum here; Jesaja Weinberg, director of the Museum of the Diaspora in Tel Aviv; Harvard professor Erich Goldhagen, a Holocaust survivor, and Sister Mary Glynn of the Bishop Kearney High School in Brooklyn.

So far the council has not decided whether to commission a separate work of sculpture or other art, according to Naftalin.