WASHINGTON (AP) -- Policies that give minorities a leg up on white college applicants are unconstitutional discrimination and should be struck down by the Supreme Court, the Bush administration argued as it formally weighed into a politically charged affirmative action case.

In twin filings to the high court late Thursday, President Bush's top Supreme Court lawyer said policies at the University of Michigan and its law school fail the constitutional test of equal protection for all under the law, and ignore race-neutral alternatives that could boost minority presence on campuses.

The admissions policies also cannot be reconciled with previous Supreme Court rulings that severely limit the use of race as a factor in government decisions, Solicitor General Theodore Olson wrote, saying the university's current policy "operates as a disguised racial quota."

"If the university genuinely seeks candidates with diverse experiences and viewpoints, it can focus on numerous race-neutral factors, including a history of overcoming disadvantage, geographic origin, socio-economic status" or other factors, Olson wrote.

The friend-of-the-court filing breaks little legal ground. It restates the constitutional case against quotas, but skirts the larger question of whether race may ever be considered as a factor in government decisions.

Thursday's filings do not go as far as some of Bush's most conservative supporters had hoped. The president is in the position of trying to please both his conservative political base and the Hispanic and black voters the Republican Party hopes to attract.

In announcing Wednesday that his administration would file briefs in the Michigan case on Thursday, Bush said he strongly supported diversity, including racial diversity in higher education. But, he added, "the method used by the University of Michigan to achieve this important goal is fundamentally flawed."

Applicants for Michigan's undergraduate classes are scored by points, with minorities or some poor applicants receiving a boost of 20 points on a scale of 150. At the law school, admissions officers use a looser formula that tries to make sure that each class has a "critical mass" of about 10 percent or 12 percent minority enrollment.

"On its face, the 20-point race-based bonus automatically added to the selection index scores of all preferred minority applicants, without regard to their background, academic performance or life experiences, is plainly unconstitutional," the administration said.

Olson pointed to admissions systems in Texas, Florida and California as alternatives. Those states do not use affirmative action yet have assembled racially diverse student bodies, he said.

The Texas plan, which Bush championed as Texas governor, offers public university admission to the top 10 percent of graduates from each high school. That assured a stream of minority applicants, because many Texas high schools are largely black or Hispanic.

Affirmative action backers say such plans do not work across the board, because not every state or community has majority-black or Hispanic high schools.

In Thursday's filing, the administration did not stake a categorical position against any use of race in university admissions, and did not ask the court to overturn an affirmative action ruling that for 25 years has allowed some role for an applicant's race.

The case marks the court's first statement on racial preference programs in public university admissions since the 1978 Bakke case, when the court outlawed racial quotas in university admissions, but left room for race to be a "plus factor." Michigan and many other public universities have used the ruling to design programs that can help minorities who might be rejected if only test scores and grades are considered.

The administration is not a party to the Michigan fight and did not have to take any position. Affirmative action, however, is the most watched issue before the high court this year and it would have been unusual for the White House to remain on the sidelines.

Thursday was the deadline for filing court papers in the Michigan case, coming close behind the awkward, racially charged exit of Sen. Trent Lott, R-Miss., as the Senate's Republican leader. Bush condemned remarks Lott made last month that seemed to long for the days of segregation.

The high court could do what the Bush friend-of-the-court brief did not and conclude race can never be a factor when a government-funded school decides whom to let in.

The court could also redraw the rules for when race may be considered. The court will hear arguments on the cases in March and a ruling is expected by summer.

The cases are Grutter v. Bollinger, 02-241 and Gratz v. Bollinger, 02-516.