...JOHANNESBURG (S&P Global Ratings) May 23, 2017--S&P Global Ratings today assigned its 'B' long-term issue rating to the proposed senior unsecured notes issued by United Bank for Africa Plc (UBA; B/Stable/B). We rate these proposed notes in line with our counterparty credit ratings on UBA. UBA operates in the top tier of the competitive Nigerian banking sector, benefitting from a sound franchise in the corporate and retail segments in its country of domicile. We also note that UBA enjoys some geographic diversification thanks to operations in 18 other African countries. As at Dec. 31, 2016, UBA had total assets of Nigerian naira (NGN) 3.5 trillion, which is equivalent to US$11.5 billion using an NGN305/US$1 exchange rate. We estimate our risk-adjusted capital (RAC) ratio for the bank before adjustments for diversification at 5.2% for year-end 2016. We project that the RAC ratio will remain broadly stable over the next 12-18 months, owing to the bank's good earning capacity and expected stable...