Undaunted by recent turbulence in the financial markets, Visa Inc., the nation’s biggest credit card network, said Monday that it would forge ahead with what would be the largest initial public stock offering in United States history.

Visa plans to sell as much as $17.1 billion of stock in late March, following in the footsteps of its smaller rival, MasterCard, which went public in May 2006.

Visa and MasterCard are prospering as Americans increasingly flex plastic, rather than use cash, to pay for just about everything. The companies have not been hurt by the credit squeeze, because they do not actually make credit card loans; they merely process transactions for banks that do.

If all goes as planned, Visa’s offering would generate a windfall for thousands of its so-called member banks, which own the company. The largest gains would go to many of the nation’s biggest banks, which have been stung by losses stemming from mortgage-linked investments.