Manila, however, faces a more ambiguous position from Washington over the claims in the South China Sea that it disputes with China and other regional countries.

Those differences help, in part, explain some of the swift moving military diplomacy now unfolding across the region.

Last weekend, Philippines Defence Minister Voltaire Gazmin emerged from discussions with US officials to talk up the need for an increased US military presence as a South China Sea deterrent, specifying possible rotations of US surveillance planes and new combat ships.

US officials, however, were much more guarded, insisting that talks were preliminary and repeatedly stressing they would not seek to rebuild bases in the Philippines.

'It's all a bit of a diplomatic dance, really,' said a veteran Asian envoy. 'The Philippines is pushing for greater commitments, and while the US is keen, they don't want to trap themselves. The bottom line is that they still need to remain ambiguous about their role in case of real trouble.'

Various articles of the 1951 defence treaty between the countries are far from clear about the South China Sea and its Spratlys archipelago, pledging consultations and mutual defence 'in the Pacific area'.

Some scholars are unsure whether it can be extended to areas of the South China Sea claimed and or occupied after 1951.

As tensions spiked in the middle of last year amid Manila's protests of incursions by Chinese vessels, Philippines Foreign Secretary Albert De Rosario insisted the treaty covered its South China Sea claims.

His US counterpart Hillary Clinton was far less emphatic. Clinton said Washington was committed to the defence of the Philippines, but on the specific issue of a Chinese attack near the Spratly islands, she refused to be drawn on 'hypothetical events'. Clinton, however, had been far more explicit a few months earlier when questioned about Chinese-Japanese tensions over the Diaoyus-Senkakus, which are currently administered by Japan.

'Let me say clearly again the Senkakus fall within the scope of Article 5 of the 1960 US-Japan Treaty of Mutual Co-operation and Security,' she said in October 2010- remarks that drew immediate fire from Beijing. Foreign ministry spokesman Ma Zhaoxu said China expressed 'its serious concern and strong dissatisfaction' at the remarks.

The ministry also swiftly protested Japan's naming exercise this week, with a spokesman saying that 'any unilateral action by Japan over the Diaoyus would be illegal and void'.

Clinton's statement marked a quiet diplomatic victory for Tokyo, which had been pushing Washington hard for an unequivocal statement. Once Clinton made it, officials in Manila started wondering whether they could also push for a stronger line in Washington.

'We had a good look... but it was clear we were never going to get such a statement, given the terms of our particular treaty,' a senior Philippines diplomat said recently. 'The Japanese treaty is clear about areas under Japanese administration. For us, robust deterrence laced with strategic ambiguity remains the order of the day, I'm afraid.'

Amid the diplomatic shadow-play, the actual deployments of surveillance planes will be closely watched by Beijing, and across the region. An ageing workhorse, the P-3C Orions being discussed are not the best weapons in the US surveillance fleet that includes drones, U-2 jets and satellites, but they still provide important low-level coverage. They can monitor electronic signals and also play a key anti-submarine role.

Their role is also symbolic. Several regional diplomats note that the US could have easily increased deployments through the Philippines with little fanfare. But deterrence, they note, has to be seen to be effective.