NEW YORK (Bloomberg) — The US dollar's share of global currency reserves fell in the second quarter to the lowest level in a decade as the holdings of euros rose to a record, an International Monetary Fund report showed.

The dollar's share dropped to 62.8 percent in the period ended June 30 from 65 percent the prior quarter, the IMF said yesterday. The euro's share rose to 27.5 percent from 25.9 percent. Holdings of British pounds gained to 4.3 percent from four percent, and the yen's share increased to 3.1 percent from 2.9 percent, the IMF said.

For the American currency, it was the lowest amount held by central banks worldwide since 1999, when Europe's common currency was first issued and the IMF started releasing quarterly figures.

World Bank President Robert Zoellick has cautioned US officials not to take the dollar's leading role as the main reserve currency for granted.

"The dollar today, of course, remains the predominant reserve currency, but nothing's guaranteed," Zoellick said in a Bloomberg Television interview in Washington.

Total foreign-exchange reserves increased in the second quarter to $6.8 trillion from $6.5 trillion in the first three months of the year. The figures on currency allocations are based on a smaller total - $4.3 trillion from April through June versus $4.1 trillion a quarter earlier - because not all central banks agree to identify the breakdown of their reserves.

The dollar's value dropped 6.2 percent in the second quarter this year, the steepest quarterly decline since the first three months of 2008, according to an index measuring it against the euro, yen, pound, Canadian dollar, Swiss franc and Swedish krona.