Credit rating agency Standard & Poor's has given the United States AAA rating a negative outlook, downgrading it from 'stable'.

Kathleen Brooks, research director at Forex.com, said the AAA rating was 'now at risk' and could be cut within two years.

She said, 'Although this comes as a shock to the markets and they experienced a knee jerk reaction in the immediate aftermath, it  isn’t that surprising.

'S&P had warned the US on its credit rating back in January when it said its top rating was at risk.'
 
Brooks said the decision could have been prompted by its growing deficit and difficulties in passing its budget.

She added, 'The dollar dived, stock futures also took a leg lower adding to pressure already on risky assets.

'Gold has had a tremendous move higher and is flirting with $1,500, as it benefits from its play as a safe haven and as a currency replacement.'
 
The perception of the US as a 'safe haven' may now be challenged, said Brooks, warning of a shift of attention away from Europe's public finances.

'In the long-term this is euro positive as German bunds  attract safe haven flows. Indeed today we have seen German 109 –year bund yields come off sharply after the announcement,' she said.

'But for now, this is only likely to spook markets more, making risk assets less attractive, safe havens like gold and the Swissie in high demand and it should keep the pressure on the dollar crosses.'