Chinese Premier Wen Jiabao said Tuesday he was deeply worried about the world economy, vowing to take flexible and prompt measures amid the changing economic environment.

I myself watch very closely the development in the world economy and the U.S. economy, and I’m deeply worried,” said Wen at a press conference after the annual session of the National People’s Congress (NPC), the top legislature.

He attributed the recent fluctuations of world stock markets to the U.S. sub-prime crisis, which led to the depreciation of the U.S. dollar and interest rate cuts by the U.S. government, as well as high international oil prices.

“What concerns me now is that the U.S. dollar is depreciating continuously, when will the U.S. dollar reach the bottom in this depreciation process, what kind of monetary policy will the U.S. government adopt and where is the U.S. economy heading?” said Wen.