The US is developing new military tactics to deter China's slow but steady territorial advances in the South China Sea, including more aggressive use of surveillance aircraft and naval operations near contested areas.
The rethink comes in the wake of the series of low-level incursions China has used to shift the status quo in one of the vital waterways of the global economy.
The challenge for the US military is to find tactics to deter these small-scale Chinese moves without escalating particular disputes into a broader military conflict. Every year, $5,300bn of goods cross the South China Sea by ship.
"Our efforts to deter China [in the South China Sea] have clearly not worked," said a senior US official.
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The growing tensions in the South China Sea, which include disputes between China and Vietnam and the Philippines, cast a shadow over the annual meeting between senior US and Chinese officials, known as the Strategic and Economic Dialogue, which started in Beijing on Wednesday.
The US delegation, led by Secretary of State John Kerry and Treasury Secretary Jack Lew, face the delicate task of trying to shore up an increasingly fragile relationship with Beijing, while laying out American concerns about Chinese maritime expansionism and cyber theft. For their part, the Chinese are irked by US moves to prosecute Chinese military officials over alleged cyber-hacking and by American alliances in Asia which Beijing views as a form of containment.
One element of the emerging US strategy was evident in March when the US flew P-8A surveillance planes over the Second Thomas Shoal, an uninhabited atoll in the South China Sea. Chinese ships there were trying to prevent the Philippines from supplying marines who were trying to get essential supplies to a ship that in 1999 was deliberately run aground on a land-feature claimed by both countries. The US planes flew at low altitude to make sure they were visible to the Chinese.
"This is a new dynamic," said a former Pentagon official familiar with the operation. "The message is, 'we know what you are doing, your actions will have consequences and that we have the capacity and the will and we are here'."
More extensive use of surveillance aircraft in the region could be coupled with a greater willingness to publicise images or videos of Chinese maritime activity. Some US officials believe the Chinese might be given pause for thought if images of their vessels harassing Vietnamese of Filipino fisherman were to be broadcast.
The US military's Hawaii-based Pacific command has also been asked to co-ordinate the development of a regional system of maritime information, which would allow governments in the western Pacific detailed information about the location of vessels in the region. Several governments say they have been caught unawares by the surprise appearance of Chinese ships.
The US has supplied the Philippines, Japan and other countries in the region with improved radar equipment and other monitoring systems and is now looking for ways to build this information into a broader regional network that shares the data.
The Pentagon has also been working on plans for calculated shows of force, such as the flight of B-52s over the East China Sea last year after China declared an exclusive air defence zone over the area. The potential options involve sending naval vessels close to disputed areas.
US officials say that there is little appetite within the administration for some of the more confrontational ideas that have been proposed as a means of deterring China. These include deploying the US coast guard to the South China Sea to counter the activities of Chinese civilian vessels and using US-led convoys to escort fisherman from the Philippines and other nations into areas where they have been expelled by the Chinese.
The Obama administration declared South China Sea a US "national interest" in 2010. Since then it has watched China take effective control in 2012 of Scarborough Shoal, 120 nautical miles west of the Philippines' main island, Luzon. As well as the altercation at the Second Thomas Shoal this year, Manila has accused Beijing of reclaiming land for a runway in a disputed area while China has also placed an oil rig in waters also claimed by Vietnam.
Despite Chinese complaints, the US has long conducted aerial surveillance in the region, although the use of its new generation of P-8A planes in contested areas represents an intensification of the activity.
Bonnie Glaser, an Asia expert at the Center for Strategic and International Studies, said that the surveillance flights showed that the US "has an interest in peaceful resolution of these disputes and opposes China's coercion". However, she added: "I'm sceptical such flights will deter Chinese behaviour."
The Philippines wants to increase its surveillance capabilities to help it shine the spotlight on what it sees as provocative Chinese actions in the South China Sea.
One Philippine official said the military intended to buy two surveillance aircraft, which was one of its highest priorities, and that it preferred planes to drones. "We need the US now while we are building a minimum credible defence," the official said.
— By Geoff Dyer and Richard McGregor in Washington and Demetri Sevastopulo in Hong Kong, the Financial Times