By Nerijus Adomaitis, Terje Solsvik and Gabriela Baczynska OSLO/BRUSSELS (Reuters) -NATO Secretary-General Jens Stoltenberg said on Thursday he will extend his term as head of the alliance by a year as it faces the “biggest security crisis in a generation” due to the war in Ukraine. Stoltenberg’s term had been set to expire on Oct. 1 and he had been due to take up a post as central bank governor of his native Norway by the end of 2022. “Honoured by the decision of #NATO Heads of State and Government to extend my term as Secretary General until 30 September 2023,” Stoltenberg tweeted. “As we fa…