Mr Wen, who was speaking to Condoleezza Rice, the visiting US secretary of state, also said he hoped the US subprime crisis would be overcome quickly, according to a statement released by the Chinese foreign ministry on Monday night.
Coming a week before the G8 summit in Japan, when both US and Chinese currency policies will be debated, the remarks are the second time this year that Mr Wen has publicly voiced unease about the weakness of the US dollar, which some economists believe has contributed to global inflationary pressures.
In recent weeks a number of Chinese officials have made statements about the problems caused by the dollar¡¯s decline.
However, China is likely to come under renewed pressure to accelerate the pace of renminbi appreciation at the G8 summit, which it has been invited to attend along with the leaders of several other developing countries including India and Brazil.
Since it abandoned its peg to the US dollar in 2005, the Chinese renminbi has strengthened by about 20 per cent against the US dollar, including a period of relatively rapid appreciation in the first quarter of this year. However, in the same period it has weakened against the euro, much to the displeasure of Brussels.
At a meeting of finance ministers in Mexico last week, Dominique Strauss-Kahn, managing director of the International Monetary Fund, said that the renminbi was ¡°substantially undervalued¡±.
He added: ¡°Obviously the valuation of the renminbi is not the only cause of global imbalances, but it is part of it.¡±
At his annual press conference in March, Mr Wen said he was ¡°deeply worried¡± about the state of the US and global economies. ¡°What concerns me now is the continuous depreciation of the US dollar and when the dollar will hit rock bottom,¡± he told reporters.
Since then, the debate within China over currency policy has become even more heated. While many officials believe that a stronger currency is one of the most effective ways of limiting inflationary pressures in the economy, state media have recently given a lot of attention to the impact of rising costs on the export sector, where a large number of small factories have been forced to close this year.
After allowing relatively rapid appreciation against the dollar in the first quarter, the central bank halted the process for most of April before permitting modest strengthening from mid-May.
Some economists believe the authorities have tried to inject more uncertainty into the market in order to discourage large inflows of speculative capital.
However, others believe the central bank has shifted its focus of foreign exchange policy from the US dollar to a basket of currencies of its main trading partners.