Tradehill Inc., an exchange for virtual currencies such as Bitcoin, is temporarily suspending trading, citing unspecified banking and regulatory reasons.

"This decision has not been made lightly and we regret having to take such action," the company said today on its website. "However, we embrace the silver lining of our situation and plan to take this opportunity to upgrade, improve, and polish our trading platform."

Tradehill has been seeking more business from investors and financial institutions as it works to legitimize virtual-currency trading in the U.S. Created four years ago by a person or group using the name Satoshi Nakamoto, Bitcoin is a virtual currency that can be used to buy and sell a broad range of items — from cupcakes to electronics to illegal narcotics.