No officer or employee of the Government may create or authorize an obligation in excess of the funds available, or in advance of appropriations (Anti-Deficiency Act, 31 U.S.C. 1341), unless otherwise authorized by law. Before executing any contract, the contracting officer shall (a) obtain written assurance from responsible fiscal authority that adequate funds are available or (b) expressly condition the contract upon availability of funds in accordance with 32.703-2.