SAN FRANCISO — Banking experts warned California leaders on Thursday that launching a state-operated public bank to serve a burgeoning, legalized marijuana industry may not be a workable solution.

Officials from Massachusetts and Colorado, states that have considered opening public banks but have not done so, told the treasurer's Cannabis Banking Working Group meeting in Los Angeles that the multi­billion-dollar capitalization costs and limited service options associated with such institutions pose major roadblocks.

“I would suggest you really do not underestimate the challenges, complexity and time requirements of these sorts of issues,” said Don Childears, president and CEO of the Colorado Bankers Association. “They are enormous for a normal bank. They're absolutely ominous for the kind of first-time-ever decisions that need to be made in a public bank.”