BEIJING -- China's top banking regulator issued a sharp critique of U.S. financial management only hours before President Barack Obama commenced his first visit to the Asian giant, highlighting economic and trade tensions that threaten to overshadow the trip.

Liu Mingkang, chairman of the China Banking Regulatory Commission, said that a weak U.S. dollar and low U.S. interest rates had led to "massive speculation" that was inflating asset bubbles around the world. It has created "unavoidable risks for the recovery of the global economy, especially emerging economies," Mr. Liu said. The situation is "seriously impacting global asset prices and encouraging speculation in stock and property markets."

Early Monday, a spokesman for China's Ministry of Commerce added further criticism of the Obama administration, targeting recent measures by Washington against Chinese exports. "We've always known the U.S. and the West as free market economies. But now we're seeing a protectionist side," the spokesman, Yao Jian, told a monthly press briefing. Mr. Yao also rejected criticism of China's currency policy, saying the yuan's exchange rate has little to do with trade imbalances with the U.S. and that China should keep the exchange rate stable.

The Chinese comments signaled that Mr. Obama -- on the third leg of a four-country Asian tour -- can expect blunt talk from Chinese leaders on the economy. The issue could complicate his broad agenda in China that also includes efforts to extract new commitments on climate change and to encourage them to take a more active role to defuse nuclear threats in Iran and North Korea.

Before heading to China, Mr. Obama underscored the urgency of his agenda on Iran by joining Russian President Dmitry Medvedev in warning Tehran that "we are now running out of time."