Nasdaq markets are still the best place for a company to raise money despite the rapid rise of the initial coin offering (ICO) in the cryptocurrency world, the vice chairman of the U.S. stock exchange told CNBC on Tuesday.

Speaking to CNBC on the sidelines of the Web Summit technology conference in Lisbon, Portugal, Nasdaq Vice Chair Bruce Aust played down the threat of ICOs.

"We are a regulated market, I think that's the difference between us and an ICO. And we'll see at some point those markets become regulated and that will change everything," Aust said.

"It's very young and early stage and Nasdaq has always been at the forefront of helping companies raise capital, whether it be in the Nasdaq private market or through the Nasdaq public markets. So we believe that we are the market for companies to raise capital."

An ICO is when a company issues a digital coin or token in exchange for a cryptocurrency in order to raise cash. The people who invest typically don't get an equity stake in the company, but can trade the coin on an exchange or use it to do something with the company.

It bears some similarities to initial public offerings (IPO), where an investors buys shares in a company. But with an IPO, a person often has a stake in the company. Because of this, some have seen ICOs as a potential threat to the IPO model. But they remain unregulated.

The ICO market is still tiny compared to the IPO market. Companies have raised around $3.2 billion so far this year from ICOs, according to Coinschedule, a website that tracks this information. In comparison, companies have raised $126.9 billion via IPOs up to the end of the third quarter, a recent study by EY shows.

Many have also poured cold water on the fundraising method. Wikipedia founder Jimmy Wales told CNBC in a recent interview that ICOs are an "absolute scam." And regulators in China and South Korea have slapped outright bans on ICOs. However, authorities in other jurisdictions, such as Abu Dhabi in the United Arab Emirates, are looking to bring ICOs into the regulatory fold.