China cancelled a visit to Washington by a senior general, slapped an indefinite ban on port calls by US naval vessels, and cancelled low-level diplomatic exchanges with the US today, in angry retaliation to a US plan to sell $6.5bn in advanced weaponry to Taiwan.
A spokesman for China's foreign ministry in Beijing, Qin Gang, said the US move broke international law and would cast a shadow over bilateral relations. The proposed sale "has contaminated the sound atmosphere for our military relations and gravely jeopardised China's national security", Qin said.
China regards Taiwan, which has enjoyed de facto independence since 1949, as a renegade province. But its aim to unify the island with the mainland is opposed by a majority of Taiwanese. Under a 1979 law, the US in effect pledged to help Taiwan defend itself against any attempt by China to forcibly acquire the territory.
A Pentagon spokesman described China's reaction to the sale as "unfortunate" and said it would lead to missed opportunities. But both sides appeared to be anxious to limit the fallout from the row. US-China cooperation on nuclear proliferation issues in Iran and North Korea was not expected to be affected.
The arms sale was first proposed by the US in 2001 but ran into opposition in Taiwan's parliament, the Legislative Yuan, as well as in Beijing. It was initially valued at $12bn and potentially included Aegis-class frigates, submarines and advanced F16 fighter jets.
The current package is much less ambitious, consisting of defensive weapons systems. It includes 330 Patriot ground-to-air missiles, 30 Apache helicopters, 182 Javelin anti-tank missiles and spare parts for Taiwan's existing fleet of F16 fighters. The Pentagon also announced a sale of Harpoon missiles last month.
China has rapidly expanded its overall military spending in recent years and has deployed an estimated 1,000 missiles across the strategic Taiwan Strait, facing Taiwan.
Prickly US relations with Taiwan have eased since the election as president last March of the nationalist Kuomintang party (KMT) leader and former Taipei mayor, Ma Ying-jeou.
Ma's predecessor as president, the Democratic Progressive party's (DPP) Chen Shui-bian, angered Washington and Beijing by pushing what both saw as a destabilising pro-independence agenda. That may have led to an undeclared freeze on new arms sales.
Ma has taken a series of steps to improve cross-straits relations since taking office, including direct charter flights for businesspeople and tourists, a lifting of caps on Taiwanese investment in China, and the opening of permanent representative offices in both countries.
Taiwan also provided assistance to China during last May's Sichuan earthquake disaster.
As a result of the thaw, Chen Yun-lin, the top official in charge of China's Taiwan policy, is expected to visit the island soon. If it takes place, it will be the highest-level contact since 1949.
All the same, Ma's popularity has been falling amid DPP criticism that he was kow-towing to China and failing to obtain reciprocal concessions. His decision to risk China's displeasure and go ahead with the arms purchase may help him counter perceptions of undue servility towards the mainland.
"We think this announcement from the US government is a sign that the past eight years of discord are over," Ma said in a statement.
According to a report last month by the Congressional Research Service (CRS), a US decision on the sale had been expected before the Bush administration leaves office in January.
Defence analysts suggested the White House wanted to push the deal through now rather than leave the decision to the incoming, possibly Democratic administration.
Embroiled in major conflicts in the Middle East, Washington has been keen to defuse cross-straits tensions and persuade the Taiwanese to take more responsibility for their own defence.
Yet now this appears to be happening, there are signs of second thoughts. According to the CRS report, a closer relationship between China and Taiwan "may complicate US regional interests".
Simon Tisdall