Central banks around the world increased their foreign currency holdings by $413 billion in the second quarter, the most since at least 2003, according to data compiled by Bloomberg News. But 63% of that new cash was put into currencies other than the dollar. That's a record-high percentage for any quarter with more than an $80 billion increase in holdings.

The dollar's 37% share of new reserves is down from about a 63% average a decade ago.

"Global central banks are getting more serious about diversification, whereas in the past they used to just talk about it," Steven Englander, a former Federal Reserve researcher who is now the chief U.S. currency strategist at Barclays PLC (NYSE ADR: BCS), told Bloomberg. "It looks like they are really backing away from the dollar."

Englander predicts the U.S. dollar will drop another 3.3% over the next three months.

Developing countries have sold about $30 billion for euros, yen and other currencies each month since March, according to strategists at Bank of America-Merrill Lynch.

Not surprisingly, China – the United States' largest creditor – has been the greenback's most vocal critic. China doesn't report its foreign currency holdings, but is thought to hold about $800 billion in U.S. debt.

Zhou Xiaochuan, Governor of the People's Bank of China (PBC), in March released an essay entitled "Reform of the International Monetary System" on the PBC Web site.

Without explicitly mentioning the U.S. dollar, Zhou asked what kind of international reserve currency the world needs to secure global financial stability and facilitate economic growth.

Zhou called for the "re-establishment of a new and widely accepted reserve currency with a stable valuation" to replace the U.S. dollar – a credit-based national currency. The central bank governor noted that the International Monetary Fund's (IMF) Special Drawing Right (SDR) should be given special consideration.

And it was reported just last week that China and the world's top oil producers are secretly planning to stop using the U.S. dollar for oil trade.

The new plan allegedly being hatched would end the dollar's role in oil trade and replace it with a basket of currencies that includes the Japanese yen, Chinese yuan, the euro, gold, and a new unified currency that would be shared by nations in the Gulf Cooperation Council (GCC). The GCC includes Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates (UAE). Together, these Gulf nations hold more than $2 trillion in U.S.