Russia is not considering a nuclear strike in its conflict with the West over Ukraine, but the Russian nuclear doctrine is a “living instrument” that could change depending on the circumstances, President Vladimir Putin said on Friday. Putin, speaking at an economic forum in St Petersburg, said his country would only use nuclear weapons in extreme situations and these these have not yet occurred, “We have no need to think about this issue,” the Russian leader told the 27th St Petersburg International Economic Forum (SPIEF). Russia could carry out nuclear tests, but for the time being there is …