In a statement, MasterCard - the US's second-largest credit card firm after Visa - says after the offering investors will own 49% of the company's equity and 83% of its voting rights.

MasterCard's 1400 member financial institutions will retain 41% of equity interest in the company through non-voting Class B common stock. They will also receive Class M common stock which has no economic rights but will allow them to elect several directors.

Based on an SEC filing earlier this year, MasterCard's largest current shareholders are JP Morgan Chase (11.7%), Citigroup (6.2%), Bank of America (6%), Euro Kartensysteme (5.2%) and Europay France (5.0%).

Craig Maurer, an analyst at Fulcrum Global Partners in New York, estimates MasterCard's total value at $7 billion - just under 2.5 times projected revenue for 2005.

MasterCard says it plans to use part of the IPO net proceeds to redeem Class B common shares from its member banks.

A new charitable foundation will receive the remaining voting rights and Class A shares representing 10% of total equity.

The company also plans to establish a majority of independent directors on its board.

The move comes as Mastercard and rival network Visa face increasing competition for bank business from independent operators like American Express and Discover. Regulatory and judiciary scrutiny of the card band's rules and regulations have further weakened the advantages of the co-operative structure, and exposed banking shareholders to financial loss from class action lawsuits.

MasterCard's progress in the IPO will be watched with interest by Visa and other bank-backed co-operative networks, including financial messaging outfit Swift.