China claims most of the South China Sea, through which $5 trillion in ship-borne trade passes every year.
US Secretary of State John Kerry on Thursday accused China of restricting navigation and overflights in the disputed South China Sea, despite giving assurances that such movements would not be impeded.
Addressing a regional meeting in Kuala Lumpur that has been dominated by the South China Sea, Kerry said China's construction of facilities for "military purposes" on man-made islands was raising tensions and risked "militarisation" by other claimant states.
Kerry's blunt criticism of Beijing, in front of his Chinese counterpart Wang Yi, is likely to put the South China Sea at the top of the agenda when Chinese President Xi Jinping visits Washington next month, experts said.
"Freedom of navigation and overflight are among the essential pillars of international maritime law," Kerry told the East Asia Summit attended by foreign ministers from around the region. "Despite assurances that these freedoms would be respected, we have seen warnings issued and restrictions attempted in recent months," Kerry said.
"Let me be clear: The United States will not accept restrictions on freedom of navigation and overflight, or other lawful uses of the sea." China has repeatedly warned Philippine military aircraft away from the artificial islands in the Spratly archipelago of the South China Sea, Philippine military officials have said.
The Chinese navy also issued eight warnings to the crew of a US P8-A Poseidon surveillance aircraft when it conducted overflights in the area in May, according to CNN, which was aboard the US aircraft.
China claims most of the South China Sea, through which $5 trillion in ship-borne trade passes every year. The Philippines, Vietnam, Malaysia, Taiwan and Brunei also have overlapping claims. There was no immediate reaction from Chinese officials to Kerry's criticism, some of his strongest yet over the issue.
China says the outposts in the Spratlys will have undefined military purposes, as well as help with maritime search and rescue, disaster relief and navigation. Wang said on Wednesday that Beijing had halted land reclamation and that the Association of Southeast Asian Nations (ASEAN) and China shared a desire to resolve the thorny issue through dialogue.
In June, China said it would soon complete some of its reclamation, while adding it would continue to build facilities on the man-made islands.
COMMITMENT NOT "FULSOME"
Kerry said he hoped China had stopped island building, but that what was needed was an end to "militarisation". He added that Wang's commitment to resolving the South China Sea issue had not been as "fulsome" as some had hoped.
"In my meeting with ... Wang Yi, he indicated I think a different readiness of China to try to resolve some of this, though I think it was still not as fulsome as many of us would like to see," Kerry later told reporters.
"But it's a beginning, and it may open up some opportunity for conversation on this in months ahead. We'll have to wait and see." Kerry said he had urged all claimants to make a joint commitment to halt further land reclamation and construction of new facilities or militarisation on disputed features.
Carl Thayer, a South China Sea expert at Canberra's Australian Defence Force Academy, said while Washington was "upping the ante", Kerry's words had to be followed through with actions. "China has already stopped construction. They're building the infrastructure," said Thayer. "China is slowly excising the maritime heart from Southeast Asia."
Recent satellite images show China has almost finished building a 3,000-metre-long (10,000-foot) airstrip on one of its seven new islands in the Spratlys. The airstrip will be long enough to accommodate most Chinese military aircraft, security experts have said.
Meanwhile, ASEAN said some members had "serious concerns" about land reclamation in the South China Sea, according to a draft of the final communique to be issued at the end of their separate talks in Kuala Lumpur this week and seen by Reuters.
Members states had wrangled hard before finally agreeing on the wording of the communique. The communique is expected to say that South China Sea matters were extensively discussed. It will also say that China and ASEAN countries would proceed to the "next stage" of consultations on a code of conduct that is intended to bind them to detailed rules of behaviour at sea.
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