Analysis By Steve Schifferes BBC News Online at the Supreme Court in Washington

It was a unanimous 1954 court decision, Brown v Board of Education, that set the American civil rights movement into motion.

Civil rights campaigners had demonstrated outside the Supreme Court

That decision began a process of school desegretion that lasted 20 years, eventually reaching the university sector.

With education seen as more and more crucial to economic achievement, the controversy over the use of race as a factor in university admission has become increasingly bitter.

Now, by a single vote, the Supreme Court has upheld the right of universities to use race as a factor in admission, upholding the broad thrust of its last ruling on the issue in 1978.

It was a decision hailed by civil rights groups, who had feared that the Court - and the country - was turning away from the gains of the civil rights era.

Effective participation by members of all racial and ethnic groups in the civic life of our nation is essential if the dream of one nation, indivisible, is to be realised Justice Sandra Day O'Connor

"This is an historic victory," said NAACP chief counsel Theodore Shaw, "which allows the long, slow, steady path of integration to continue."

Given how deeply affirmative action is ingrained in American life, not just in universities but also in companies, a complete reversal would have meant a huge upheaval.

The influence of minority groups in the US is also growing as they increase in size, with one-third of US citizens now members of minority groups, compared to one-fifth when the civil rights era began.

Echoing the words of Brown, Justice Sandra Day O'Connor wrote for the majority:

"Effective participation by members of all racial and ethnic groups in the civic life of our nation is essential if the dream of one nation, indivisible, is to be realised."

And perhaps decisive for the court was the brief filed by the American military academies, who argued that it was essential to take race into account when selecting officers for the Army, in order to ensure that there were enough non-white officers leading black and Hispanic soldiers.

Narrowing the scope

But the Court also significantly narrowed the scope of such affirmative action plans, making it more risky for universities to design programmes that they can sure are not seen as illegal quotas.

Jennifer Gratz (right) complained about Michigan's admission system

And even the majority decision, written by Justice Sandra Day O'Connor, warned that the use of race to enhance diversity had to be limited in time, and said "the Court expects that 25 years from now, the use of racial preferences will no longer be necessary."

The narrowness of the verdict will stimulate activists on both sides to redouble their actions to continue to change the law.

Terry Pell, president of the Centre for Individual Rights, which brought the case, said that the way was now open for state legislatures to ban the use of racial preferences in public university admissions.

"Today's split doubleheader seems perversely designed to prolong the controversy," wrote Justice Antonin Scalia, who opposes affirmative action.

Retiring justices?

The closeness of the vote means that there are high stakes indeed over future appointments to the court.

Both Chief Justice Rehnquist, who wrote the majority decision outlawing quotas in the undergraduate case, and Justice O'Connor, who upheld the law school affirmative action programme, are rumoured to be considering retiring from the court on grounds of age and illness.

If President Bush were to replace the key swing vote, Justice O'Connor, with a more conservative justice, it could well tip the balance both on civil rights cases and on abortion rights, where the court has so far upheld the right of women to terminate their pregnancies.

That will increase the concerns of Democrats, who are already at odds with the president over his selection of several lower court justices, whom they see as too conservative.

President Bush had opposed affirmative action, and the US Government filed a brief arguing that universities should not use race as a factor in admissions.

This could be important in the forthcoming 2004 election, as there is little doubt that affirmative action is unpopular in many parts of the country, especially the South.

The Republicans are hoping to reinforce their grip on Presidential votes in Southern states, including the closely fought state of Florida.

And they are hoping to pick up several vulnerable Senate seats in the South, improving their wafer-thin majority in the Senate.

It is precisely because of the political controversy that it has been the Supreme Court, not the Congress, that has taken the lead in such issues as civil rights and abortion.

Now, it appears, just a single vote is preserving that traditional role of the Supreme Court.