Most US banks shun people like Hope Wiseman, who runs a dispensary that sells marijuana for medical use.

But a bill designed to open up banking to those in the pot industry, such as herself, is sparking optimism as it makes its way through Congress.

Wiseman, who operates a dispensary called Mary and Main, in Capitol Heights, Maryland, just outside Washington, serves patients who suffer from migraine headaches, chronic illnesses or depression.

She feels lucky to already have an account at a bank, but says she is at the facility's mercy, since it could close it at any time.

Marijuana for medical use is legal in 33 states and the US capital of Washington, 12 of which have also legalized it for recreational use.

But under federal law, pot is still classified as a hard drug, just like cocaine. Most banks fear being charged with money laundering if they work with people in the legal marijuana industry.

Wiseman's bank is one of few that accept merchants like her as customers.

"We are charged very high fees because the business is so special, and we are just subject to their mercy," said Wiseman, who opened her dispensary last year.

Transactions are carried out mainly in cash, and when the money is deposited it takes several days to show up in her account, making it difficult to pay bills and employees' wages.

Wiseman's debit card only works with online transfers of crypto currency. The bank will not give her a credit card, deeming her a risk. And the bank can shut down her account over the slightest suspicion that a transaction is illegal.

This wariness on the part of the banks also affects organizations that are regularly or occasionally involved with the marijuana industry.

Jenn Michelle Pedini, head of development at NORML, one of the main organizations lobbying for legalization of marijuana, said she had problems with the government when she helped a marijuana vendor set up a company under a consulting firm that she operates.

The pot industry is indeed booming, generating more than $10 billion a year in revenue which could hit $56 billion by 2025, accord to pro-legalization lobbies.

But of the 11,000 banks and other lenders operating in the United States, only 700 work with people in the marijuana sector, according to Treasury Department figures.

Last week the House of Representatives passed a bill designed to protect pot industry professionals and associated companies from running afoul of the federal government. It now goes to the Republican-controlled Senate.

Supporters of the SAFE Banking Act also say it reduces the risk of burglary and violent robbery in an industry where cash is king.

Critics of the bill say it gives drug cartels easier and less-monitored access to the financial sector.

Tanner Daniel, vice president for congressional relations at the American Bankers Association (ABA), called the bill's passage "a necessary incremental step forward."

"ABA is not taking a stance on legalization. 99 percent of members state that clarification is needed on the state and federal level," Daniel said at a recent forum in Washington.

Daniel added that 75 percent of ABA members have closed the accounts of customers potentially tied to the pot industry.

Republicans in the Senate tend to frown on use of marijuana.

Michael Correia, of marijuana lobbying group National Cannabis Industry Association, said Congress "is not ready to debate the merits of legalization."

"Politicians have been waiting for the polling and the public. It will be state, after state, after state, before the federal level," Correia said.

That is what Thiru Vignarajah, a former deputy attorney general in Maryland and candidate for mayor of Baltimore, wants to do -- legalize pot in the city, and hope the state eventually follows suit.

He also proposes taxing pot sales with a city-backed and -regulated crypto currency and using that money to invest heavily in education.

Legalization would also help in the fight against crime in Baltimore, one of the most violent cities in America, he said.

"The murder rate is among the highest in the country. The drug war between gangs is fuelling the overwhelming majority of it," Vignarajah told AFP.

He admitted, however, that pot is just part of the drug problem and legalizing it is no panacea.