In a white paper, the US Postal Service Office of Inspector General says that the post office should think about targeting the quarter of American households - 68 million adults - that are underserved by the banking industry.

With its huge physical network, the postal service is well placed to move into this area, picking up the slack left by banks shutting down their branches. However, the white paper stresses that this should not be done by becoming a bank but rather through partnerships with traditional lenders.

The paper says that payment products would be the easiest way for the postal service to get into financial services, thanks to their low costs and the chance to partner banks.

It suggests an open-loop pre-paid card that could be loaded with cash from pay cheques and then used to withdraw money from ATMs, pay bills and send remittances. By working with government it could also be used to send and receive tax payments and refunds.

The postal service should also look into online and mobile technology, letting customers check balances, transfer funds, pay bills, and deposit cheques from their computers and phones.

With underbanked Americans spending $89 billion just on interest and fees for alternative financial service in 2012, the watchdog argues that by capturing 10% of the market, the postal service could reverse the losses it has made in recent years.

Last week telco T-Mobile made its pitch for a slice of the pie with its pre-paid card and app-based product.

Several postal services around the world, including in the UK and New Zealand, have already entered the banking market and India is set to follow suit.

Having already applied to the Reserve Bank for a banking license, this week India Post began a pilot in Delhi. The organisation is rolling out ATMs at post offices that will offer core services and hopes to have 300 machines installed around the country within 18 months.