DETROIT — The University of Michigan announced yesterday that it will comply with a new voter-approved ban on affirmative action and immediately stop considering race and gender in admissions.

The move came in the middle of the admissions process for next fall’s freshman class. The university has already begun sending out acceptance and rejection letters.

The state constitutional amendment approved by the voters in November bans the use of race and gender preferences in public university admissions and government hiring and contracting.

After it passed, the university put its admission process on hold and asked the courts that it be given until this summer to comply with the ban, saying it would be too disruptive to change its policies now. But a federal appeals court said no.

“We cannot sustain any further delay in our admissions process without harming our ability to enroll a class of students for the 2007–08 academic year,” Teresa Sullivan, executive vice president of academic affairs.

The university will continue its legal challenge of the measure in the meantime, Ms. Sullivan said.

“This is a big step forward, there’s no doubt about it. It’s good news,” said Terence Pell, president of the Center for Individual Rights, a group that sued to force immediate compliance with the ban. “It’s a watershed moment.”

The university said it would use other criteria that are not explicitly race- or gender-based to achieve diversity.