BRUSSELS (Reuters) – NATO accused Russian President Vladimir Putin on Friday of provoking “the most serious escalation” of the war in Ukraine since it began, but said he would not succeed in deterring the alliance from supporting Kyiv. “We have the combination of the mobilisation in Russia, combined with the reckless, dangerous nuclear rhetoric, and then today’s illegal annexation, or attempt to annex parts of Ukraine,” NATO Secretary General Jens Stoltenberg said. “Together this is the most serious escalation of the conflict since the start and the aim of President Putin is to deter us from s…