Citibank says its cash machine, debit card and online banking network is back online after a two-day outage caused by computer software failures.
A Citibank spokesman, Mark Rodgers, told the Associated Press that normal service had been resumed after unspecified "internal software issues" brought the system crashing down.
The problems first surfaced in the bank's 2000-strong ATM network on Tuesday afternoon, as demand for cash peaked after the Labor Day holiday weekend. Online banking services for 750,000 customers were also disrupted as the bank scrambled to uncover the source of the failures.
Citi mobilised an extra 500 branch staff during the downtime and has promised to refund fees charged to customers who were forced to use rival bank networks.
Citibank's embarrassment follows a similar disruption at Australia's Westpac, which was forced to shut down its Internet banking system for five days recently to deal with software failures.