Apple will allow software developers include virtual-currency transactions in their applications. "Apps may facilitate transmission of approved virtual currencies provided that they do so in compliance with all state and federal laws for the territories in which the app functions," Apple said in an update to its App Store review guidelines.

It is not clear whether Apple refers to Bitcoin or any other future form of virtual currency.

Virtual currencies are not backed by any government or central bank and are bought and sold on a peer-to-peer network independent of central control.

U.S. state regulators are looking to toughen rules on the use of the virtual currencies as they see risks associated with them.

Last week, satellite TV operator Dish Network said it would accept bitcoin payments from customers from the third quarter.