Former spokesmen for Romney had no immediate comment on the administration's decision. But Sen. Charles Schumer, a longtime critic of China's trade policies, criticized it.
"This report all but admits China's currency is being manipulated but stops short of saying so explicitly," Schumer, D-N.Y., said in a statement. "It's time for the Obama administration to rip off the Band-aid and force China to play by the same rules as all other nations."
Treasury said the yuan, also known as the renminbi, has risen in valued by 9.7 percent since June 2010 — and by 12.6 percent when inflation is taken into account.
Still, Treasury said the yuan remains significantly undervalued. It vowed to keep pressing Beijing to let the currency rise further to "level the playing field for American workers and businesses and support a strong, sustainable and balanced global economy."
The U.S. trade deficit with China reached $29.1 billion in September. It is running 6.8 percent ahead of last year's record pace. It has long been the largest U.S. trade gap with any one country.