The irresistible force of US political power is on collision course over the yuan's exchange rate with the immoveable object that is Chinese sovereignty. Which will prevail and when is still anyone's guess.
The economic logic for a loosening of the yuan's decade-old peg against the dollar might be overwhelming given China's bulging balance-of-payments surplus. Washington's ultimatum to China to loosen the link or be declared a currency manipulator in six months' time, risking trade penalties, is also crystal clear.
Yet what is far from obvious is that China, a proud nation with an acute sense of its own national interest, will give in.
"The pressure could have the opposite effect to what the United States wants," said Gao Huiqing, a senior economist at the State Information Centre, a top government think-tank in Beijing.
"This is no longer a pure economic issue," Mr Gao said of the debate over the yuan. "It has been turned into a political issue. China is unlikely to back down."
Alert to Chinese sensitivities, US Treasury Secretary John Snow praised China last week for the steps it has taken to prepare the ground for a more flexible yuan and said Washington was looking for an "intermediate" step, not an immediate free float. Although Mr Snow brandishes a big stick, China will be aware that, in some ways, he is acting from a position of weakness.
Unless he can persuade China to make an initial move on currency reform, Mr Snow risks seeing Congress seize the initiative from the Treasury on international financial policy.
A Senate bill would impose a tax on Chinese imports of 27.5 per cent, the degree to which the measure's sponsors say the yuan is undervalued, if China refuses to end the yuan's peg of 8.28 per dollar. "In order to get Congress out of the picture, the US administration needs to say their way is working. In order for them to say that their way is working, China's got to deliver something on the yuan revaluation front," said Tim Condon with ING Financial Markets in Singapore.
Chinese policy makers are pragmatists, and they might very well unshackle the yuan in the near future. The central bank governor said last month all the political and technical preparations for a shift had been completed. But there was no mistaking Premier Wen Jiabao's prickliness when he declared last week to a US business delegation that it was China's sovereign right to decide its exchange rate policy.
"Politically, the Chinese don't want to be seen to be bowing to foreign pressure because that would reduce their legitimacy at home," said Lai Hongyi, a research fellow at the National University of Singapore's East Asia Institute.
"The US tends to favour a very public, pressure-cooker style of diplomacy. Other developed countries such as the European Union or Australia follow a more subtle approach, and that works better for the Chinese," Mr Lai said.
Setting aside the politics, he said China had every reason to tread carefully. Japan, he noted, bowed in the 1980s to US pressure to revalue the yen and paid a heavy price.
Asset prices shot up, only to collapse in a deflationary heap, ushering in a decade of stagnation, deflation and a full-blown banking crisis.
China was running less risk than Japan had run then of a boom and bust in asset prices, but its banks were in much worse shape, Mr Lai said.
"If the Chinese banking system collapsed, that would be a real danger for China, first, and also for the US and for the region," he said.
The risk that a stronger yuan would suck in agricultural imports, threatening the livelihood of millions of peasants, is also a paramount concern for China's Communist rulers, intent as they are on preserving social stability, analysts say.