Donald Trump has criticized Bitcoin, Facebook’s proposed Libra digital coin and other cryptocurrencies and demanded that companies seek a banking charter and make themselves subject to US and global regulations if they wanted to “become a bank”.

“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, the White House, the Federal Reserve and the treasury department did not immediately respond to requests for comment.

Trump’s comments come one day after the Federal Reserve chairman, Jerome Powell, told lawmakers that Facebook’s plan to build a digital currency called Libra cannot move forward unless it addresses concerns over privacy, money laundering, consumer protection and financial stability.

Powell said the Fed has established a working group to follow the project and is coordinating with other government’s central banks. The US Financial Stability Oversight Council, a panel of regulators that identifies risks to the financial system, is also expected to make a review.

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

JPMorgan Chase & Co, the largest US bank by assets, plans to launch its own digital coins.

Bitcoin, the best-known digital coin, was created in 2008 as an alternative to currencies controlled by governments and banks, but crypto trading and digital currencies remain largely unsupervised. The market has also faced allegations of money laundering and terrorist financing.