While Bitcoin and other cryptocurrencies have gained mainstream notoriety, it remains unlikely any Bitcoin exchange traded fund (ETF) will appear on the New York Stock Exchange any time soon.

That prediction comes from Tom Farley, the president of NYSE Group that oversees the New York Stock Exchange. While speaking with Bloomberg at the World Economic Forum’s annual meeting in Davos, Switzerland, Farley said Bitcoin ETFs still have a ways to go before clearing the necessary regulatory hurdles.

Bitcoin The president of the NYSE says there won't be a Bitcoin ETF on the stock exchange any time soon.

I saw a message that said this is not a mature asset class in the vein of the U.S. dollar or gold,” the president of NYSE Group said Thursday. “If I had to guess, it’s a while. I don’t have timing, but it is not imminent.”

There have been a number of efforts to get a Bitcoin ETF off the ground, along with gain similar acceptance for other cryptocurrencies but none of the attempts have proven successful thus far, falling short of gaining approval from the United States Securities and Exchange Commission.

Perhaps the most notable failure thus far was the Winklevoss Bitcoin Trust ETF, backed by twin entrepreneurs Cameron and Tyler Winklevoss of Facebook fame. The effort was rejected by the commission after it found the proposed fund was susceptible to fraud due to the digital currency’s unregulated nature.

The concept behind the Winklevoss ETF and others like it is to create a stock fund tied to the price of Bitcoin (or another cryptocurrency), which would allow investors to purchase the currency without holding it directly. The fund would work in the same way that a person can investment money into another commodity like gold.

ETFs would have helped lower the barrier of entry that comes with the cryptocurrency, which can require some technical know-how. Currently, acquiring cryptocurrency requires people to create a unique bitcoin wallet and the ability to “mine” for bitcoin by lending their computing power to blockchain transactions.

Investors in a bitcoin ETF wouldn’t be able to make purchases using Bitcoin but would be able to buy and sell it at its listed value, which would benefit the cryptocurrency economy by creating more liquidity in the market.

The SEC is still approaching cryptocurrencies with a critical eye. Earlier this month, the commission raised a number of investor protection concerns about cryptocurrency mutual funds and ETFs in a letter to industry groups.

In the letter, the SEC asked questions about the potential for currency manipulation, challenges regarding setting an accurate value for a product tied to volatile markets, and how demand to redeem the virtual currency would be met, among other questions.

Farley said he saw the letter as a message from the SEC that meant the commission intended to “take it slow” with Bitcoin and other cryptocurrencies. “This is not yet a mature asset class in the vein of, let’s say the U.S. dollar or gold. It’s a journey from collectible baseball cards... to gold. Bitcoin has left the collectible baseball cards but isn’t quite at gold.”