Citigroup Inc raised its estimates and now expects to issue $18 billion to $21 billion in long-term debt in 2010, the company said in a regulatory filing on Friday.

Citigroup now expects to raise about $3 billion to $6 billion more in long-term debt, excluding local country debt, than it previously estimated for the year.

The $18 billion to $21 billion of expected long-term debt issuance compares with the $35 billion of expected maturities during the year, Citigroup said in the filing.

The company raised its estimates as part of its efforts to maintain and solidify its structural liquidity, as well as extend the duration of liabilities supporting its businesses, the filing said.

Citigroup said it is continuing to review its funding and liquidity needs and it may adjust its expected issuances for the remainder of 2010 due to market conditions or regulatory requirements.

(Reporting by Maria Aspan; editing by Andre Grenon)