The reluctance to weaken the currency comes after China's capital and financial account recorded a deficit of $91.2 billion in the last quarter of last year, and the country's foreign exchange regulator, the State Administration of Foreign Exchange (SAFE), warned that capital flows would be volatile this year.
A weaker yuan could accelerate capital outflows, taking a further toll on economic growth, which is already expected to grind to a 25-year low this year, and SAFE has also indicated that the exchange rate could be fixed to counter shocks to the economy.
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First-quarter GDP figures on Wednesday are likely to confirm China's "new normal" of slower growth, but policy options to help the economy are restricted by Beijing's desire to avoid the kind of asset bubbles that followed its stimulus measures in response to the global financial crisis. It also wants to press on with reforms that will eventually make the economy more efficient, but could in the short term make things difficult for the bloated state sector.
Eddie Cheung, a strategist at Standard Chartered in Hong Kong, said China had in recent months increased its efforts to support its currency, in part to wrongfoot investors who were betting on a persistently weak yuan.
"All central banks, not just the People's Bank of China, are worried when the market gets too one-sided, so they want to smooth out the volatility," Cheung said.
And China's plans to internationalize its currency by lobbying for its inclusion in the International Monetary Fund's (IMF) special drawing rights (SDR) basket may also have played a part in the yuan's recent strength, Cheung said.
The SDR, an international reserve asset, currently comprises dollars, yen, pounds and euros. The basket is up for review in May, and Chinese Premier Li Keqiang was reported by state news agency Xinhua as saying last month that he had asked the IMF to include the yuan in the SDR.