NATO Defense Financing Act This bill authorizes the President to make direct loans to countries that joined the North Atlantic Treaty Organization (NATO) after March 1, 1999, for the purchase of U.S. defense articles. The President may (1) make such loans with lower interest rates than required by statute, and (2) charge fees associated with such loans. Before making such a loan, the Department of State shall certify to Congress that the receiving country (1) is making demonstrable progress toward meeting its NATO defense-spending obligations, (2) is respecting the country's constitution and upholding democratic values, and (3) has demonstrated a commitment to a free market economy and the capacity to meet the loan's terms.