By Steve Schifferes BBC News Online Washington correspondent

The US Government is to join in a court action to block universities from taking race into account when making admissions decisions.

President George W Bush has announced that the federal government is joining a group of white students from the University of Michigan who are suing because black and Hispanic applicants are given extra points towards admission.

They have to decide whether they're for civil rights and diversity or not Tom Daschle, Senate Democratic leader

The president called the Michigan admission plan "divisive, unfair, and impossible to square with the US Constitution."

He said that it amounted to a quota, and was fundamentally flawed, while he called on all Americans to work against racial prejudice.

The Supreme Court will rule on the case later this year, and the government will file a brief outlining its own concerns to the court.

The move will reignite controversy over the Republicans' attitude towards race relations.

In December the Republican Senate leader, Trent Lott, was forced to resign for making remarks that appeared to support the battle for segregation in the South.

Republicans and race

Civil rights groups and Democrats are upset by the Bush administration's stance.

The leader of the Senate Democrats, Tom Daschle called the move on affirmative action a watershed for the Bush administration.

The challenge is to focus on diversity in ways that do not use quotas Presidential spokesman Ari Fleischer

"They have to decide whether they're for civil rights and diversity or not," he said.

But the president's spokesman, Ari Fleischer, disagreed.

"He wants to find a way to recognise the importance of diversity, and do so in a way that serves one and all," he said.

"The challenge is to focus on diversity in ways that do not use quotas."

The president has backed an approach he adopted when he was governor of Texas.

That would give the automatic right of admission to students in the top 10% of their high school class, which could help schools in poor neighbourhoods with a largely minority student body.

This "affirmative access", he said, which is also used in Florida and California, has increased minority access to education and diversity without using quotas.

Backing off Bakke

The issue of affirmative action in education has been a central part of the US civil rights struggle, since the US Supreme Court case in 1954 which ordered public schools to desegregate.

George W Bush attended Yale like his father

At the university level, efforts to have a fixed quota of minority places were blocked by another court decision known as Bakke in 1978.

But universities were still able to take race into account when making admission decisions by saying they were giving due consideration to encouraging "diversity" in their student body.

At the University of Michigan, minority students were given an extra 20 points on a 150 point scale used to rate their suitability for admission - more than they received for high test scores.

The Southern strategy

The decision by the Supreme Court when it comes will have widespread political ramifications.

And the Republicans face the biggest dilemma on the issue.

One the one hand they have been increasing their appeal in the South, and among conservatives who oppose affirmative action.

They won control of the Senate in November partly by unexpectedly picking up seats in Georgia and very nearly in Louisiana.

On the other hand, Mr Bush has been stressing the need for his administration to reach out to minority groups as part of his philosophy of "compassionate Conservatism".

Recently he praised the efforts of black welfare mothers to move into jobs through training and education.

Reports suggest that the president's key political advisor, Karl Rove, had been arguing for a more moderate approach to the issue, stressing the need to reach out to Hispanic voters in the 2004 presidential election.