Add the CEO of Swiss banking giant UBS to the "blockchain not bitcoin" crowd.

In a new interview with CNBC this week, Sergio Ermotti expressed doubt about cryptocurrencies, stating that the role of the technology still "needs to be defined."

However, he was more bullish on private distributed ledger technologies, noting his company has already invested in a partnership with IBM to run international trade transactions on a blockchain.

He told CNBC:

With the remarks, Ermotti joins other financial sector luminaries, such as Jamie Dimon and Warren Buffett, who have recently cast doubt on both bitcoin and the cryptocurrency asset class more broadly. Although, he perhaps hinted most at the divide between permissionless blockchain technologies, like bitcoin, and bank-sponsored alternatives.

UBS and IBM's joint project, for example, is called Batavia, and it has been built on the open-source Hyperledger Fabric framework.

IBM announced that Bank of Montreal, CaixaBank, Commerzbank and Erste Group had all also joined the project earlier this month.

Photo via Remy Steinegger at World Economic Forum