Russia is a little nervous that Chinese railway building to Central Asia might pose a threat under different conditions:
China is offering to build new railroads into Central Asia. This is part of a $300 billion plan to upgrade and expand Chinese railways over the next two decades. Chinese businesses are investing more billions to create new businesses in Central Asia and the cheapest way to get goods in or out of this landlocked area is via rail. ...
Something Russia does not like to discuss openly is the fact that Chinese railroads extending into Central Asia would make it easier for China to carry out major military operations in the area.
Like I've said, I want China to pivot to Asia.