Islands illegally built by China in Vietnam’s Truong Sa archipelago (Photo: EPA)

Spokesman for the US Department of State, John Kirby, told the media on Monday that China’s activities have worsened the situation.

Senator John McCain, Chairman of the US Senate Armed Services Committee, said China has pursued its territorial ambition including landing planes on Chu Thap reef in Truong Sa archipelago. He criticized the Obama administration for delaying further "freedom of navigation" patrols within 12 nautical miles of the islands built by China in the East Sea.

Last Saturday, Pooja Jhunjhunwala, spokesperson for the US Department of State, said China’s action has increased tension in the region. He urged all parties to halt unilateral moves that harm regional stability and security and create conditions for effective diplomatic measures.  

At a press conference on Monday, Japanese Foreign Minister Fumio Kishida said Japan is concerned over China’s unilateral action to change the status quo in the East Sea. He said Japan will not accept activities to escalate regional tension and will work with relevant countries to protect freedom of navigation.