WASHINGTON, Sept. 10 (Reuters) — The Senate voted today to block proposed changes in student aid rules that critics say would deny federal assistance to thousands of students even as tuition costs at the nation's universities surge.

The Republican-controlled Senate voted 51 to 44 to approve a Democratic amendment that would bar the Bush administration from making changes to the student aid formulas for the first time in a decade. The provision was attached to a $139 billion spending bill financing health, labor and education programs, which passed later tonight, 94-0.

Senator Jon Corzine, the New Jersey Democrat who sponsored the amendment, said the changes would have cost at least 84,000 college students their eligibility for financial aid, with many more facing much reduced levels of federal assistance.

"These changes come at a time when tuition is rising dramatically," Mr. Corzine said. "Tinkering around with the formula is going to end up undermining the ability of literally hundreds of thousands of middle-class Americans to have access to financial aid grants and loans."

The Department of Education has said the revisions were required by law and would significantly affect only a small number of students.

The Senate also agreed to increase spending on education for children with learning disabilities by $1.2 billion in 2004.