The only case where you cooperate with the designated enemy
Is when there is an even bigger enemy to deal with.
Russia is the designated enemy. It never stopped being so. In the last 30 years USA, UK and to a lesser extent some other NATO countries invested billions into regime change operations, "freedom fighters" of the variety that take children primary schools hostage, propaganda, media, political parties - anything you can think of. In vain - in fact it backfired. If we just left them alone in the 1990-es the natural course of events would have taken course and they would have been ruled by an adorable drunk while slowly slipping into irrelevance off the world's stage. They would have handed their nukes for more loans and more bribes to the ruling class by now just the way Ukraine did.
But no, we had to keep poking the wasps nest and instead of an adorable drunk we have Putin, T14 Armata tanks, Circon/Bramos-2 hypersonic missiles and plenty of other toys like Leader class nuclear destroyers enqueued in the pipeline. And just to make things clear - we are the designated enemy on their side.
So, back on the topic. The only way these two sides will grudgingly agree to share toys is if some green lizard men from Gliese enter orbit tomorrow and we need to deal with a bigger threat.