...HONG KONG (S&P Global Ratings) May 28, 2018--S&P Global Ratings today said it has assigned its '##' long-term issue rating to the Swiss franc-denominated senior unsecured notes due 2023 issued by Korea National Oil Corp. (KNOC; ##/Stable/--). The issue rating is subject to our review of the final issuance documentation. KNOC plans to use the proceeds to refinance its debt obligations. Our rating on KNOC is equalized with the sovereign credit ratings on South Korea (##/Stable/A-1+) because we expect an almost certain likelihood of extraordinary government support if the company were to suffer financial distress. Wholly owned by the government, KNOC plays a critical role as the sole policy arm for managing the country's strategic petroleum reserves and improving its oil self-sufficiency. As of end-2017, KNOC's capital structure consisted of about Korean won (KRW) 9.7 trillion of unsecured debt at the parent level, and about KRW0.7 trillion of secured debt and about KRW2.8 trillion of unsecured...