Beijing: Beijing`s claim to almost the whole of the South China Sea is "problematic" and the Asian power`s actions have raised tensions, a US official said today on the eve of high-stakes talks.
China also disputes islands with Japan - a US security ally that Washington is treaty-bound to defend if attacked - and officials travelling with Secretary of State John Kerry said they had "heightened concerns" about "the readiness of claimants to utilise military, paramilitary, coastguard forces in furtherance of their claims".
Kerry arrived in Beijing today for the sixth Strategic and Economic Dialogue, billed as the main annual meeting between the world`s two largest economies.
The two days of tough discussions will seek to chart a path ahead in turbulent China-US ties roiled by differences over Asia-Pacific maritime tensions, Internet hacking and trade issues.
China`s claim to the strategic South China Sea - also claimed in part by the Philippines and Vietnam, among others - is based on a line drawn on 20th century maps.
A US official travelling with Kerry said: "The ambiguity associated with the nine-dash line is problematic."
China and its neighbours in the region have stepped up their patrols of disputed areas, and recent spats have led to ramming incidents, the use of water cannon and arrests of fishermen.
The heightened tensions are "very relevant to the United States as a Pacific power, as a major trading nation, as an important consumer of the sea lanes and as a long-term guarantor of stability in the Asia Pacific region," the senior US administration official said.
The official spoke anonymously in order to candidly discuss the talks, and added that the conversation will be held in "a very direct, candid, and constructive way".
The US stresses that it takes no sides in the territorial claims, but has accused Beijing of destabilising acts and urged it to uphold freedom of navigation in the key waterways.
China has stressed it is committed to diplomatic, peaceful means to address the claims, the US official said. "We want China to honour that and live up to its word."
Other issues high on the agenda include North Korea, following a "significant" visit last week by Chinese President Xi Jinping to Seoul.
"There is a steady convergence in the views between the US and China on both the importance and the urgency in moving North Korea to take irreversible steps to denuclearise," the official said.
But while Beijing`s patience with the brinkmanship of its wayward, unpredictable ally appears to be wearing thin, it has not publicly shown any willingness to take any action towards the regime.
Kerry is to meet with Xi on Thursday.