The obvious solution would be not to go to war with china/russia unless they shut down energy exports. And of course they wouldn't, as they depend on selling and also importing electricity at times. We even have practical experiences with that. Germany for many decades got their natural gas from the sovjet union and russia. Despite of the cold war, and it indeed was just short of a war state, gas supplies never were cut. Because cutting gas supply to Germany would have been a simple way to apply pressure, but not a cheap one. It would either have triggered a war or at minimum that after recovering from the cut, Germany would have been permanentely lost as a trading partner. So there was never a supply cut in many decades.