Citigroup is set to raise a further $3 billion (£1.5 billion) by issuing new shares to shore up its balance sheet, after already tapping investors for $6 billion earlier this month.

The new share issue will take the total America's largest bank has raised since the beginning of the year to $41 billion, including $32 billion from sovereign wealth funds.

Since the US sub-prime mortgage crisis emerged in the US, Citigroup has been one of the worst-hit of the investment banks, writing off more than $33 billion on the value of its assets since the third quarter of last year, cutting 9,000 jobs and replacing its chief executive, Charles Prince, with Vikram Pandit.

Commenting on the latest fundraising, Gary Crittenden, chief financial officer at Citigroup, said: "We are issuing common equity at this time as we continue to optimise our capital structure.

"We're pleased with the strong interest we have already received regarding this issuance."

However some analysts expressed surprise that the latest round of capital raising amounted to just $3 billion.

Oppenheimer, the US brokerage, said: “By our estimates, we believe Citi needs to raise an additional $10 billion to $15 billion or sell several hundreds of billions worth of assets in order to truly shore up its capital position.”

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