The fine is being disputed as too high and Citi shareholders have said they issued less mortgage-backed securities than Bank of America and JPMorgan.
Large Citi shareholders said that they preferred to fight in court instead of paying the $10bn fine, while last week Citigroup offered less than $4bn to resolve the situation.
In the UK Citigroup bought sub-prime lender Future Mortgages for around £40m in 2001 but it closed after the crash.
Last year JPMorgan agreed to pay a $13bn settlement for misleading investors on the quality of mortgage-backed securities.
This is similar to the Bank of America scenario where they offered just $12bn to settle allegations after $17bn was requested.
