So the Appropriations have to come through Congress as the House controls the pursestrings, not out of an a fund governed by the Executive.

USE OF FUND SUBJECT TO APPROPRIATIONS.—The authority of the Secretary of Defense to use the Fund under this section in any fiscal year is subject to the availability of appropriations for that purpose.

https://www.govinfo.gov/content/pkg/USCODE-2010-title10/pdf/USCODE-2010-title10-subtitleA-partIV-chap148-subchapII-sec2508.pdf