use, with or without reimbursement, any service, equipment, personnel, or facility of any Federal agency with the explicit support of that agency, to the extent such use does not impair or conflict with the authority of the President or the Administrator of the Federal Emergency Management Agency under the Robert T. Stafford Disaster Relief and Emergency Assistance Act (
42 U.S.C. 5121 et seq.) to direct Federal agencies in any major disaster or emergency declared under that Act; and