The United States of America has expressed its concern to China over its support for the Russian defense sphere, reports Voice of America. It is noted that this issue was discussed by US Deputy Secretary of State Kurt Campbell with China’s Executive Vice Foreign Minister Ma Zhaoxu on March 27. The conversation revolved around Beijing’s support for Moscow’s defense-industrial base. According to a State Department representative, this phone call is part of ongoing efforts to maintain open lines of communication between the United States and China. China-Russia relations China has begun to streng…