India's Supreme Court has rejected a plea by the federal government to allow controversial affirmative action quotas in colleges and universities.
Under the government's plan the lower castes' share of places in educational institutions would more than double to nearly 50%.
The court, which had put the programme on hold until August, extended its decision to the end of this year.
Correspondents say the move has split the country.
Many argue the plan 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
Putting the programme on hold in March, the Supreme Court 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.
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.
Earlier this year, the government 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.