Obama's statement on US debt.
Here is a CBS News article describing the Chinese concern.
U.S. Debt Worries China
America's Largest Foreign Creditor Concerned Its Massive Holdings Will Plummet In Recession
(AP) China's premier expressed concern Friday about its massive holdings of Treasuries and other U.S. debt, appealing to Washington to safeguard their value, and said Beijing is ready to expand its stimulus if the economy worsens.
Premier Wen Jiabao noted that Beijing is the biggest foreign creditor to the United States and called on Washington to see that its response to the global slowdown does not damage the value of Chinese holdings.
"We have made a huge amount of loans to the United States. Of course we are concerned about the safety of our assets. To be honest, I'm a little bit worried," Wen said at a news conference following the closing of China's annual legislative session. "I would like to call on the United States to honor its words, stay a credible nation and ensure the safety of Chinese assets." (excerpt) read more at cbsnews.com