(CNN) A bipartisan group of attorneys general from 33 states and five territories are urging Congress to advance a bill that would allow cannabis businesses access to the federal banking system.

While several states have legalized medical or recreational marijuana, the substance is still illegal under federal law. Banks providing services to state-approved cannabis businesses could face criminal and civil liability under some banking statutes, so cannabis companies resort to operating on cash.

The Secure and Fair Enforcement Banking Act, known as the SAFE Banking Act , would provide protections for banks that work with marijuana companies.

"Our banking system must be flexible enough to address the needs of businesses in the various states and territories, with state and territorial input, while protecting the interests of the federal government. This includes a banking system for marijuana-related businesses that is both responsive and effective in meeting the demands of our economy," the National Association of Attorneys General, led by the Colorado attorney general, wrote in a letter to Congress Wednesday.

They point to the growth of the marijuana industry and argue that the SAFE Banking Act would bring billions of dollars into the banking sector.

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