Harvard University's undergraduate admissions programme does not discriminate against Asian-American applicants, a federal judge ruled on Tuesday, rejecting a lawsuit brought by opponents of affirmative action and backed by the Trump administration.

The lawsuit was brought by a group hoping to eventually overturn United States Supreme Court precedents that allow colleges to consider race as one factor in admissions, so long as quotas are not involved.

US District Judge Allison Burroughs in Boston concluded that Harvard's programme survived strict legal scrutiny, and advanced the Ivy League school's interest in having a diverse student body.

"The court will not dismantle a very fine admissions programme that passes constitutional muster, solely because it could do better," Burroughs, an appointee of former President Barack Obama, wrote in a 130-page decision.

Students for Fair Admissions (SFFA), a group founded by affirmative action opponent Edward Blum, had accused Harvard of engaging in illegal racial balancing.

SFFA said Harvard's policies limited Asian-Americans to no more than 20 per cent of incoming classes, and left them less likely to be admitted than white, black and Hispanic applicants with comparable qualifications.

Blum said SFFA was disappointed with Burroughs' decision, will ask the federal appeals court in Boston to reverse it, and if necessary will seek Supreme Court review.

“The documents, emails, data analysis and depositions SFFA presented at trial compellingly revealed Harvard's systematic discrimination against Asian-American applicants,” he said.

Harvard did not immediately respond to requests for comment.

Burroughs ruled nearly a year after a non-jury trial.

If the case eventually reached the Supreme Court, that body, which now has a five-member conservative majority, could use it to bar or more strictly limit affirmative action in college admissions.

The court has allowed affirmative action in several decisions, including its landmark 1978 ruling in Regents of the University of California v. Bakke, which allowed race to be considered in college admissions.

'Not there yet'

SFFA had contended that while Asian-American applicants to Harvard often outperformed on academic measures, stereotyping caused many to receive low scores on personal ratings.

Those ratings are designed to reflect admission officers' assessments of how applicants might contribute to the Harvard community.

Harvard denied the charge, saying its use of race in admissions was not a factor in the personal ratings.

The US Department of Justice sided with SFFA, saying Harvard's policy significantly disadvantaged Asian-Americans, and that the university had not seriously considered race-neutral approaches to admissions.

It has also probed whether another Ivy League school, Yale University, also discriminates against Asian-Americans.

Burroughs agreed with Harvard that the university had no "workable and available race-neutral alternatives" to ensure a diverse student body while preserving its high academic standards.

She also rejected the argument that Harvard's undergraduate admissions were the functional equivalent of quotas or racial balancing that the Supreme Court has rejected.

Burroughs said Harvard's programme was not perfect, and that the school could improved bias training for admissions officers, maintain clear guidelines on using race in admissions, and do a better job of flagging race-related disparities in its ratings.

She concluded by noting Supreme Court Justice Sandra Day O'Connor's prediction in a 2003 decision upholding an affirmative action programme at the University of Michigan that such policies would likely not be needed within 25 years. That prediction has often been criticised by conservatives.

Diversity at Harvard and other schools "will foster the tolerance, acceptance and understanding that will ultimately make race-conscious admissions obsolete", Burroughs wrote.

She said people will eventually view race as "a fact, but not the defining fact and not the fact that tells us what is important, but we are not there yet. Until we are, race conscious admissions programs that survive strict scrutiny will have an important place in society."