"I am not a fan of Bitcoin and other Cryptocurrencies, which are not money, and whose value is highly volatile and based on thin air," Trump wrote on Twitter.

"If Facebook and other companies want to become a bank, they must seek a new Banking Charter and become subject to all Banking Regulations, just like other Banks, both National and International," he added.

Facebook said last month it would launch its global cryptocurrency in 2020. Facebook and 28 partners, including Mastercard Inc (MA.N), PayPal Holdings Inc (PYPL.O) and Uber Technologies Inc (UBER.N), would form the Libra Association to govern the new coin. No banks are currently part of the group.

JPMorgan Chase & Co (JPM.N), the largest U.S. bank by assets, plans to launch its own digital coins.