LONDON -- Standard&Poor's CreditWire 4/25/97 -- Standard&Poor's today has assigned its triple-`A' rating on Nippon Telegraph and Telephone Corp.'s (NTT) US$500 million 6.750% Eurobond due May 16, 2002. The rating outlook is negative. The rating is based on NTT's dominant position and important role in the Japanese telecommunications market and strong cash flow and financial profile among major international peers. Despite increased penetration by Japan's new common carriers, NTT maintains a very strong share of the domestic telephone market. Company earnings are improving as a result of successful rate rebalancing and continued growth of the Japanese cellular phone market. NTT's financial profile also remains solid. Strong internal cash flow covers a large portion of its capital