Washington — Congress may need to pump $6-billion more into the Pell Grant program next year, an increase of more than 40 percent, to meet its promise of a higher per-student benefit at a time of increased enrollments and tougher economic conditions, an Education Department official has warned.

The department calculates the Pell Grant need for the 2009 fiscal year at $20.1-billion, compared with $14.2-billion in 2008, said Thomas P. Skelly, director of budget service, in a memorandum to lawmakers.

The increased need in the main federal grant program for low-income college students was driven initially by a vote in Congress to raise the value of the maximum Pell Grant, from $4,241 to $4,310. In addition, Mr. Skelly told lawmakers, both the number of recipients and the costs are higher for the 2007-8 and 2008-9 academic years.

Estimates for 2009-10 are being driven even farther upward by trends that include “significantly higher” numbers of applicants completing the federal-aid form, more Pell-eligible students attending college, and more students qualifying for more need-based aid, he said.

Congress is likely to approve the necessary increases, said Edward M. Elmendorf, senior vice president for government relations at the American Association of State Colleges and Universities. “If it is threatened, you’ll hear about it,” he told The New York Times. “The decibel level will be deafening.” —Paul Basken