Beijing's offensive this week against Tokyo's beggar-thy-neighbour currency depreciation was, simply, masterly; it finally compelled Japan and the United States to intervene and check the yen's slide. The mainland cannot claim full credit for the dramatic intervention; anxious European and Asian leaders have warned about the regional financial crisis spreading west if the two countries watched while the yen plunged. A senior World Bank official lent credence to their dire warnings, saying inaction could provoke a global slump in a matter of months. The need for an intervention by Tokyo and Washington was obvious, and the call for one was gathering momentum. Yet the two remained nonchalant until a frustrated Beijing gave the extra nudge by subtly but cleverly hinting that its repeated vow not to devalue the yuan was not cast in stone, and there was a limit to the pain it could endure from the yen fall. First, it did this by orchestrating the publication of a Xinhua news agency commentary in the big financial newspapers, lambasting Japan and the United States - the world's biggest economies - for being self-serving and exporting their economic woes abroad. On Tuesday, Minister of Finance Xiang Huaicheng - in a lengthy People's Daily commentary - warned the stability of the yuan could be threatened by failure to achieve 8 per cent growth, adding to investor fears about a possible devaluation. Beijing was playing to the hilt the role of the good guy: it still trumpeted its promise of non-devaluation - which would help prevent another round of competitive devaluations - as its contribution to regional stability. No doubt it wants to contribute and be rewarded by a speedier entry to the World Trade Organisation. Yet there is an element of self-interest - to prevent a speculative attack on the Hong Kong dollar and maintain mainlanders' confidence in the currency and the new government under Premier Zhu Rongji. Nowhere in the two commentaries did Beijing openly declare it would renege on its promise - if it could help it. But it was telling the big boys: 'I don't want to devalue, but you guys - by standing by when the yen plunged - are putting tremendous pressure on me to break the vow.' On Wednesday, Reuters quoted a vice-minister for Foreign Trade, Sun Zhenyu, as saying: 'If the change in the exchange rate puts large pressure on foreign trade and exports, or if there is a large fall in foreign trade and exports, then I am afraid we may have to consider the question of whether to make adjustment.' His words were interpreted as a threat to devalue, and the story was splashed on Reuters screens worldwide. Mr Sun later denied the story when contacted by China Daily . Denial or not, his words were read worldwide and might have contributed to his country's case for Tokyo and Washington to act. Shortly after the release of the Reuters story came news that Washington and Tokyo had intervened in the foreign exchange markets to shore up the yen. Mr Clinton reportedly met top aides, including Treasury Secretary Robert Rubin and National Security Adviser Sandy Berger, on the possibility of a yuan devaluation amid a further slide in the yen. The conclusion was clear, marking the first time the US has truly done something to help Asia since the outbreak of the crisis last summer. Mr Sun might have blundered, but he could have inadvertently done his country and the rest of Asia a great service.