The U.S. Postal Service has quietly begun offering a handful of new or expanded financial services in four cities, a potential first step toward a return to postal banking, which advocates say could help rescue the agency's finances and assist millions of people who have limited or no access to the banking system.

Tatiana Roy, a spokesperson for the Postal Service, said in an email that the pilot program — a collaboration between the Postal Service and the American Postal Workers Union — began Sept. 13 and that it aligns with the goals set out in the 10-year plan the Postal Service announced in May.

Postal banking was not explicitly called for in the plan, which Roy said would help the agency "achieve financial sustainability and service excellence," but it is a longtime desire of progressive politicians and advocates whose attempts to push it through Congress in recent years have been met with little success. It would require an act of Congress to re-establish postal banking beyond the limited services the Postal Service is beginning to test, but the pilot program could act as a proof of concept.

New services include check cashing, bill paying, ATM access, expanded and improved money orders and expanded wire transfers. Select Postal Service locations in Washington, D.C.; Falls Church, Virginia; Baltimore; and the Bronx, New York, are participating.

Mark Dimondstein, the president of the American Postal Workers Union, said the test run was "a small step in a very positive direction."

"We view expanded services as a win for the people of the country, a win for the Postal Service itself, because it will bring in new revenue, and, of course, a win for the postal workers who are extremely dedicated to the mission," Dimondstein said in a phone interview.