However, Russia and China share a long border, and have had a history of tensions. If it weren't enough that Russia is and has been paranoid about invasions, the exact border is in dispute in places, with fairly large, unreported military actions.

If those ramped up I could see it endangering cooperation on many levels, as happened with Russia and China 50 years ago.

The US and Russia don't have a common border except across the Arctic, eliminating that source of friction, anyway.

Hope they can hold it together. Would love to see a lot of robots doing science, and person or two for the collective ego.