BNP Parisbas, France’s biggest bank, is facing a hefty fine from authorities in the US.

The amount, due to be announced later, is expected to be in the region of $9 billion (6.5 billion euros).

The bank has put aside 800 million euros to cover the cost of US penalties.

Shares in BNP have fallen some 15 percent since April.

Company chief executive Jean-Laurent Bonnafe wrote a memo to staff saying: “I want to be clear, we will be punished severely.”

The fine looks set to be the third largest ever handed down to a financial institution by US authorities.

Tim Elliott, a strategist from the Devere Group, explained: “It’s a large fine. Bear in mind the bank probably made just over four billion euros last year. I think the long term trend is that all banks who want to deal in dollars on behalf of their clients are going to have to basically move their regulatory headquarters to Washington.”

BNP Paribas is accused of breaking sanctions against Iran, Cuba and Sudan.

It is alleged the bank concealed clients names from blacklisted countries when processing $30 billion through the US.