(Recasts, adds context)
NEW YORK, March 31 (Reuters) - The share of global foreign exchange reserves held in U.S. dollars fell marginally, to 64 percent from 64.4 percent, in the fourth quarter of 2008 as overall reserves dipped for the second consecutive quarter, IMF data showed on Tuesday.
The IMF data, which covers about two-thirds of the world's foreign exchange reserves, shows the dollar share of the $4.2 trillion of world reserves of which the composition is known fell to $2.69 trillion.
Evidence of a significant shift away from U.S. dollars has been erratic. Although the dollar's share has dropped from around 71 percent in 1999, the year the euro was launched, it has remained generally steady over the past five years.
"The most important take away from the IMF's quarterly reserve report is that for the second consecutive quarter, official reserves fell in Q4 08," Marc Chandler, global head of currency strategy at Brown Brothers Harriman in New York, said in a note to clients.
Currency reserves appear to have peaked in the second quarter of 2008 near $7.01 trillion, Chandler said.
The euro's share rose to 26.5 percent in the fourth quarter from 25.6 percent in the third quarter of 2008. The euro accounted for around 18.1 percent of allocated reserves at the end of the first quarter of 1999, the first period of its launch.
"There was widespread talk of intervention by numerous central banks, including Russia and a handful of Asian central banks to sell dollars," Chandler said.
By the end of 2008, the IMF estimates that global reserves stood at $6.71 trillion. Allocated reserves slipped to $4.21 trillion from $4.36 trillion in the third quarter and $4.43 trillion in the second quarter.
Unallocated reserves, thought to be largely China's, fell to $2.50 trillion in the fourth quarter from $2.53 trillion in the third quarter and $2.58 trillion in the second quarter.
The dollar bottomed against the Canadian dollar and British pound in November 2007 and against the Swiss franc in March 2008. But it was only early in the third quarter of 2008 that it bottomed against the euro, after which it rallied well into the fourth quarter, Chandler said.
The IMF's currency breakdowns provide only limited insight into shifts in the composition of central banks' holdings because they do not cover around one-third of the world's reserves.
That one-third includes several emerging economies such as China, which has the world's largest foreign reserves, approaching $2 trillion, and has surpassed Japan as the largest holder of U.S. government debt.
Investors may become more focused on the IMF data in the future after China's central bank governor said earlier this month that the world should consider the IMF's special drawing rights, a basket of dollars, euros, sterling and yen, as super sovereign currency to replace the dollar. For more detail, see: [ID:nPEK184558].
But IMF Managing Director Dominique Strauss-Kahn last week gave his full support to the dollar, saying the greenback's days as the world's top reserve currency are not over and that the Chinese believe the same. [ID:nPAB004722].
While no one is seriously considering the dollar will lose its pre-eminence anytime soon, the idea of using SDR as a reserve currency has gained momentum.
Russia this month proposed tasking the International Monetary Fund with researching the possibility of widening the list of reserve currencies, creating a new reserve currency, or using SDRs as a super reserve. [ID:nLG32185].
A United Nations panel also published a report this month that said an alternative currency system based on the SDR could help contribute to global financial stability and strength. [ID:nLI186948]. (Reporting by Nick Olivari; Additional reporting by Gertrude Chavez-Dreyfuss; Editing by Dan Grebler)