What efforts should be made to ensure the sustainability of the French public debt by 2027? The first part analyzes the French sovereign negotiable securities in terms of outstanding amounts, maturity and average coupon. These criteria examination highlights the factors of its sensitivity when the interest rates increase. The second part examines the expected Government cash-flows over the period 2017-2027 and its balance parameters according to its debt. The identification of debt securities allows to identify future funding sources based on assumptions about the Operating Public Budget, growth and inflation. The updated annual deficits generate new issuances which are analyzed in the light of how accompanying interests and redemption annual service. Both deteriorate financial equilibrium conditions. The article measures the efforts to be made in budgetary terms to ensure the sustainability of the debt within ten years, depending on whether the rates are stable or increasing.