The best stories from the Shangri-la Dialogue, Asia's leading informal defence gathering, do not come from the public utterances of high-profile figures like Secretary of Defense Chuck Hagel. Indeed, the most extraordinary thing I heard at the first full day of this year's dialogue here in Singapore came from a PLA senior colonel at a working session on maritime security.

It is common knowledge that China resents the presence of American surveillance ships and aircraft off its coast, in its 200 nautical mile exclusive economic zone (EEZ). China considers this bad for its national interest. After all, the Americans are presumably collecting data on Chinese military activities, among other things. China also presumably sees the ongoing presence as an insult to its national pride, a reminder of a history of humiliation by foreign powers.

Thus it was striking to hear a Chinese military officer reveal in an open discussion at this conference today that China had 'thought of reciprocating' by 'sending ships and planes to the US EEZ', and had in fact done so 'a few times', although not a daily basis (unlike the US presence off China).

This was news to me. It turns out, from discussions with several maritime security experts in the margins of the conference, that rumours have been circulating for some time of China sending ships on missions to waters off US territory – not the continental US, but probably Hawaii and possibly Guam too. Still, this is the first time any of us can recall this point being made on the public record.

To be precise, the Chinese officer did not say explicitly whether the Chinese ships (and/or aircraft) were collecting intelligence, or whether they were just venturing near US territory to make a political point. But it would seem odd that they would forgo the opportunity to conduct surveillance. And he did say 'reciprocating'.

Why is this revelation important? A few reasons. First, it may amount to the beginning of a Chinese realisation that its interpretation of the UN Convention on the Law of the Sea may not be in its long-term interests. That interpretation has been that freedom of navigation does not include the right to conduct surveillance in another country's EEZ. Most countries, including the US, consider such surveillance to be a peaceful activity allowed under the convention. (To be clear, all including America agree that peacetime intelligence-gathering within the 12 nautical mile limit of anyone else's territorial waters is a big no-no.)

As China's economic and strategic interests, and naval capabilities, extend ever further from its shores, perhaps some within the Chinese security establishment are anticipating future benefit from their own country having the legal right to gather intelligence in other countries' EEZs. But for now, if China is indeed conducting the occasional surveillance foray in America's EEZ, then it is in breach of its own interpretation of sea law.

Moreover, if China is admitting that it is starting to compete with America at its own game, then doesn't this also amount to an acknowledgement that the US Navy is not going to be persuaded to give up its surveillance in East Asian waters? Incidents like the harassment of the USNS Impeccable in 2009 are generally believed to have been part of a campaign to push the Americans back. Is China now recognising that that campaign has failed and that it needs to try a new tack?

If so, it might help explain why China seems less intent than a few years ago on pursuing risky encounters with American ships and planes – incidents which could conceivably have escalated to confrontation, even conflict.

It may also help explain why maritime risk-reduction talks and military-to-military dialogues between China and the US seem to be making progress. If China really is beginning to experiment with voyages by its spy ships to America's Pacific islands, perhaps that will turn out to be good news for everyone.

Photo courtesy of Chinese Military Aviation.