A diplomatic dispute between Taiwan and the Philippines intensified Thursday, as Taipei began a military exercise in the disputed waters between both countries.
The air and naval drills in the Bashi Channel come a week after the Philippines Coast Guard shot dead a 65-year-old Taiwanese fisherman, prompting outrage in Taiwan.
The family of the fisherman and Taiwanese officials have refused to meet the Philippine president's personal representative who was sent to Taiwan to apologize for the death.
Taiwan's premier Jiang Yi-huah rejected the apology of President Benigno Aquino because it referred to the shooting as "unfortunate" and "unintentional." Taiwan also rejected an earlier statement of regret by a lower-ranking official.
Taiwan has imposed sanctions on the Philippines, including recalling its envoy to Manila and freezing job permits for Philippines workers.
A State Department spokesman says the U.S. is concerned by increased tensions between two neighboring democracies and close American allies. It urges both to clarify disagreements and ensure maritime safety.
The Philippines Coast Guard said it was acting in self-defense in last Thursday's incident, because it said the fisherman's boat was about to ram the coast guard vessel. Taiwan has rejected those charges.
Taiwan and the Philippines, along with Brunei, China, Malaysia, and Vietnam all have competing claims to parts of the sea, which may be rich in oil and natural gas.