Action taken under the authorities to which this section applies, resulting in the allocation of petroleum products or electrical energy among classes of users or resulting in restrictions on use of petroleum products and electrical energy shall not be based upon unreasonable classifications of, or unreasonable differentiations between, classes of users. In making any such allocation the President, or any agency of the United States to which such authority is delegated, shall give consideration to the need to foster reciprocal and nondiscriminatory treatment by foreign countries of United States citizens engaged in commerce in those countries.