A low-level Russian diplomat who spoke at a conference in Virginia a few days ago created some stir - he was quoted by Financial Times as saying that "Russia could respond with force if the US put a "combat weapon" into space".
The Foreign Ministry spokesperson later tried to explain that the diplomat was misunderstood, but then more or less repeated his words - "If we cannot find understanding with the administration of the United States [about weapons in space] and find ourselves in a situation when we have to react, we'll certainly do it."
If this reminds you the arms-race rhetoric of the cold war it is because the Russian diplomats like to think they live in the world where this rhetoric works (alas, they are not alone). The reality is quite different - a closer look at the Russian military space program clearly shows that Russia has lost its capability to carry out serious development projects in military space and is very unlikely to recover it.
This is not to say that there are no good reasons why the U.S. plan of deploying weapons in space is a bad idea. It's just that a possible arms race with Russia is not among them.