The politically sensitive report, which examines the foreign exchange practices of major US trading partners, has repeatedly singled out China for not allowing its currency to appreciate more rapidly.
But the Obama administration and the previous Bush administration have stopped short of labeling China a currency manipulator - something Romney has vowed to do his first day in office, should he win the presidency in November.
The yuan has appreciated 30 percent since July 2005 and China argues that its currency is no longer tightly controlled.
The Treasury Department said it was delaying the report in order to "assess progress" following the group of 20 finance ministers meeting Nov. 4-5 in Mexico City. That means the report, which is often delayed, is all but assured to come out after the US presidential election Nov. 6.
The Romney campaign has said the administration should not delay the report, which is required by law to be released Oct. 15 and April 15.
Lawmakers and manufacturers have long complained that China keeps the yuan artificially low in order to give its companies a price advantage in international trade.