Central banks are shifting reserves away from the US and towards the euro zone in a move that looks set to deepen the Bush administration's difficulties in financing its ballooning current account deficit.

In actions likely to undermine the dollar's value on currency markets, 70 per cent of central bank reserve managers said they had increased their exposure to the euro over the past two years. The majority thought euro-zone money and debt markets were as attractive a destination for investment as the US.

The findings emerge from a survey of central bank reserve managers published today and conducted between September and December of last year. About 65 central banks, controlling assets worth $1,700 billion, took part and the results showed a marked change in attitude over the past two years.

Any rebalancing of central bank reserve portfolios has serious implications for the global financial system as the US has become increasingly dependent on official flows of funds to finance its current account deficit, estimated at $650 billion in 2004.

At the end of 2003, central banks held 70 per cent of their official reserves in dollar- denominated assets and central bank purchases of US securities had financed more than 80 per cent of the US current account deficit in 2003. Any reluctance to increase exposure to dollar assets further could cause the dollar to plunge on currency markets.