Congress declined last week to include a $100-million emergency appropriation for AmeriCorps, the national-service program that helps some students pay for college, in a supplemental spending bill for the current fiscal year. That marked the end of a months-long battle to secure additional funds that program advocates say are necessary to avoid large-scale cuts in the number of volunteers and participating organizations.

"Everyone in the national-service field is very disappointed that this was not approved," said Alan A. Khazei, chief executive officer of City Year, a national group that puts volunteers in poor urban areas.

Without the additional money from Congress, Mr. Khazei and other AmeriCorps supporters say, the program will be forced to shrink, even though President Bush and others want it to expand. By this fall, Congress and President Bush are expected to push legislation that would bring the number of participants in the immensely popular program up to 75,000 next year.

The $100-million would have gone toward paying for more than 20,000 volunteers that the Corporation for National and Community Service, the federal agency that runs AmeriCorps, had accepted above what it should have in 2002. To make up for that excess, the program had to delay those volunteers' enrollment for a year.

The loss of the $100-million may force the shutdown of hundreds of programs that expected those workers this year. Some states may be left with no AmeriCorps volunteers at all. Coordinators of the programs left standing say their ability to serve needy populations will be seriously weakened.

A coalition of nonprofit organizations, corporations, and members of Congress called in June for a $200-million supplemental appropriation for AmeriCorps for 2003, to pay for all of those volunteers. The Senate agreed to provide $100-million in additional appropriations, but critics in the House of Representatives blocked the money from the supplemental spending bill. The critics said that even though the program is respected for its good work in many communities, the agency has been bedeviled for years by poor management and accounting.

"Everyone in the field did the right thing," said Kyle Caldwell, chairman of the Board of Directors of America's Service Commissions, a group of state service agencies. "It's because of the broken federal bureaucracy."

Even though the door has closed on getting the $100-million in 2003, said Mr. Khazei, of City Year, there is still hope that much of the damage could be mitigated in the 2004 fiscal year, which begins October 1. That could happen if President Bush pushes his plan to expand AmeriCorps and gets Congress to approve it, he said.

AmeriCorps usually receives its money from Congress at the start of the fiscal year but does not disburse the funds to partner organizations and volunteers until late spring, Mr. Khazei explained. If the agency could start paying out its 2004 money immediately, he said, it could retain more volunteers and organizations and still have 50,000 volunteers for 2004. That would be better, he said, than having 30,000 participants in 2003 and trying to jump to 75,000 in 2004.

AmeriCorps provides money for college tuition or to repay student loans in exchange for volunteer work in local communities.