India's Supreme Court has put on hold controversial plans to boost places for lower-caste and other disadvantaged people in colleges and universities.
Under the government's affirmative action plan the lower castes' share of places in educational institutions would more than double to nearly 50%.
Correspondents say the move has split the country, with many arguing it could hurt India's rapid economic rise.
But it has the support of millions of students from underprivileged groups.
The plan to increase affirmative action quotas has been bitterly opposed by students at some of the country's best-known professional colleges
The court told the government to put the programme on hold until August.
It said the government needed to provide fresh data on lower castes - also known as Other Backward Castes or OBCs in official language - because it said it found the present data too old.
The 27% seat allocation is based on the population of OBCs in India, according to the census carried out in 1931.
Correspondents say the ruling is likely to provoke strong emotions among the people who support reservations and rejoicing among those who have been campaigning against the government attempts to introduce the measure.
Fruit of growth
Indian Prime Minister Manmohan Singh has said his government is committed to removing iniquities so that everyone can enjoy the fruit of India's economic growth.
The government has recently pushed a bill through parliament in which places at some of the country's best-known professional colleges are set aside for students from lower-caste and disadvantaged communities.
And it is considering asking the private sector to institute some kind of affirmative action and also extend the benefit to the country's Muslim minority.
A recent study suggested that India's Muslims were economically and socially worse off than Dalits.
But the move is being opposed by many who feel that it will lower standards and endanger India's economic growth.