The Philippines risks losing a case it filed against China's claims to nearly all of the South China Sea if Taiwan succeeds in convincing an international tribunal that Itu Aba, an outcrop in the Spratly archipelago, is an island and not simply a "rock", analysts here say.
"Their position is sabotaging our case," Mr Richard Javad Heydarian, a security expert at De La Salle University, told The Straits Times.
Taiwan has been on a high-profile drive to present the 46ha Itu Aba, which it has occupied since 1956 and calls Taiping, as an island.
President Ma Ying-jeou visited Itu Aba, 2,000km south of Taipei, in January. On Wednesday, international journalists were given a tour there. Following the tour, Mr Ma invited the Philippines to send government representatives to Itu Aba.
These visits have made a big show of a freshwater source on Itu Aba, where some 200 coast guard personnel and researchers live. The journalists drank water from a well and were served lunch prepared with produce grown there.
For the most part, the Philippines' case with the Permanent Court of Arbitration in The Hague discusses land features in the Spratlys, in the southern half of the South China Sea. The Philippines argues that none of the rocky outcrops in the Spratlys is an island, which has, as a defining feature, a freshwater source that can sustain a small population. Itu Aba is a rock, it insists.
The distinction is key to Manila's case: Under international law, an island is entitled to a 200 nautical mile exclusive economic zone, while it is just 12 nautical miles for a rock. If Itu Aba is considered an island, its 200 nautical mile zone will stretch all the way to the western Philippine province of Palawan.
"That will take the case out of the jurisdiction of the tribunal," said Mr Jay Batongbacal, director of the UP Institute for Maritime Affairs and Law of the Sea.
Mr Heydarian said Itu Aba may lead the tribunal to defer its ruling.
"It can say the Philippines and Taiwan will first have to settle the issue over their overlapping waters... Even this is tricky because we have a 'one China' policy."
The Philippines is asking the court in The Hague to determine the maritime entitlements of land features in the Spratlys to show that China has been illegally extending its borders by occupying reefs in the South China Sea that are 1,611km away from its nearest land mass. Given the diplomatic isolation of Taiwan, which is regarded as a Chinese province, Mr Ma's moves serve various purposes, say analysts.
"Since the South China Sea became an issue, Taiwan has been excluded from all official meetings about it, and so Mr Ma wants to take this opportunity to increase our visibility," said Dr Arthur Ding, director of the Institute of International Relations at the National Chengchi University in Taipei.
"This works to some extent because so many people now see that there is, for instance, natural water on Taiping, proving that it is an island... This could improve our chances that the judgment will go our way."
Also, with President Ma set to step down on May 20, he would want to ensure he leaves with an unequivocal statement of his efforts to keep Taiping within Taiwan's fold.The recent developments, however, leave China in an awkward position, Dr Ding noted.
On the one hand, given that China and Taiwan's claims are in parallel, any action to prove that Taiping is habitable will indirectly bolster China's claim. On the other, Taiwan is seeking to elevate its international profile by issuing the invitation to the Philippines.
All things considered, "I think China will keep silent", said Dr Ding.
• Additional reporting by Li Xueying