China's Ambassador to the United States said China has to seriously think about beefing up its defence capabilities in the region, state agency Xinhua reported, after a US warship entered waters that China claims in the South China Sea.
Mr Cui Tiankai's comments come as Chinese defence authorities accuse the US of militarising the region. Analysts say this may prompt China to follow suit, ramping up tensions further in the disputed waters.
"We have to make sure we have sufficient means to safeguard our sovereignty there, to protect our lawful rights there," Mr Cui was quoted by Xinhua as saying in a CNN interview. This would ensure that "nobody will have any more illusion that it could continue to provoke", he said.
Mr Cui said that the US was "hypocritical" in asking others not to militarise the region when it is sending military vessels there so frequently. On Tuesday, the USS Lassen entered within 12 nautical miles of Mischief and Subi reefs in the Spratlys, in a direct challenge of China's territorial claims from building islands in the area, which the US does not recognise.
Two Chinese vessels followed the US guided-missile destroyer, which left without incident. The US, however, has said that it will continue to regularly conduct such "freedom of navigation" exercises.
After confirming the episode, China's Foreign Ministry spokesman Lu Kang told reporters if the US continued to create tensions, China might conclude it had to "increase and strengthen the building up of our relevant abilities".
China has long maintained that its island-building in the South China Sea is mainly for civilian purposes, with President Xi Jinping making a pledge not to militarise the islands during his US state visit last month.
But China may change its calculations if the US increases its patrols or sends bigger vessels to challenge China's claims to the islands, said South China Sea expert Liu Feng. "China will calibrate its reaction according to US action, so increased US activity in the South China Sea might force China's hand," he told The Straits Times.
"Its vessels might become more aggressive, or it may build up its defence capabilities."
An editorial in China Daily yesterday said that the US is the real hand pushing the militarisation of the South China Sea.
The Chinese government is already facing pressure from an angry Chinese public. "We have to militarise the South China Sea," one netizen wrote on social media. "Since the US has created this opportunity, we should grab it."
Dr Li Mingjiang from the S. Rajaratnam School of International Studies believes China may increase the number of military patrols in the disputed waters, but that it cannot build much more on the islands because of limited space. China will also be mindful of the already strained relations it has with its neighbours, particularly Asean, he said.
"It will weigh these factors because it understands that its land reclamation activities have been significant," he told The Straits Times. "This isn't just about the US."
Mr Lu told reporters at a daily briefing yesterday that China and Asean have established channels for resolving differences in the South China Sea.
"We hope that countries outside the region would support, instead of disrupting efforts by China and Asean countries... It will do good to no one."