The US government has tried to integrate China into the current international system despite its strategic pivot to the east. Besides factors of containment, US policies toward China still retain a willingness to cooperate.

The diplomatic confrontation between the US and Russia is always fiercer than that between the US and China, and carries a thicker color of containment, as the US remains wary of Russia, which it believes wants to challenge and transform the existing international order.

The US government believes that Russia has expansionist and hegemonic traditions that China doesn't have. Prior to restarting bilateral relations in 2009, the US had been preventing Russia from controlling the Commonwealth of Independent States countries. After Vladimir Putin, then-prime minister, put forward a roadmap for building a Euro-Asia alliance in October 2011, the US government deemed it was a plan aimed at restoring the Soviet Union and expressed resolute resistance. This is one of the deep-rooted reasons why the US instigated the Ukrainian parliament to dismiss its pro-Russia president on Feb 22, 2014, ending Ukraine's possibility of joining the alliance.

Finally, the US government estimations of the present state, prospects and potential of Russian and Chinese economic development differ enormously. Similarly, its assessments of the respective significance of US-Russia and US-China economic and trade cooperation also diverge.

The volume of US-Russia trade was around $39 billion in 2012, and $38 billion in 2013; while that of US-China trade was $536.2 billion and $521 billion respectively. So, as US-Russia energy cooperation gradually withers, the US is no longer concerned about inflicting harm on itself while imposing sanctions on Russia. However, it is an utterly different story when it comes to China.

Therefore, US foreign policy toward China is always more complicated than its policy toward Russia. The Ukraine crisis has only further accentuated this.

The author is a professor at the Institute of Russian Studies at the Chinese Academy of Social Sciences.