NEW YORK, June 6 (Reuters) - Gemini Trust Co, the U.S.-based bitcoin exchange founded by investors Tyler and Cameron Winklevoss, has opened trading in Canada, marking the start of an international expansion program.

In an interview late on Friday, Gemini Chief Executive Officer Tyler Winklevoss said Canadian citizens would only be able to trade bitcoin and ether on the exchange for now.

Trading bitcoin and ether against fiat currencies such as the dollar will take a few weeks, Winklevoss said, adding that no regulatory approval was needed to operate in Canada.

Winklevoss said Gemini would open another international location over the next two weeks.

Digital currencies have gained popularity among investors as major financial institutions such as Goldman Sachs Group Inc and global technology companies such as International Business Machines Corp try to unlock the potential uses and applications of these assets’ underlying technology, the blockchain.

The blockchain is a database that enables a network of computers to validate, clear, settle, track, and record the ownership of assets as they are traded.

Ether, an alternative currency that differs from bitcoin, is a token or digital asset of the Ethereum platform, a public blockchain.

“We decided to open first with the bitcoin and ether order book,” said Winklevoss. “We think there’s great demand for that; there are a lot of people who own bitcoin, and they don’t have a safe place to store them.”

He added that most bitcoin and ether investors were trading on unregulated and unlicensed exchanges.

Gemini last month became the first and so far only exchange that New York state allows to trade ether, Winklevoss said.

Volume on Gemini since ether started trading on the exchange has grown steadily, he said.

“Over the last 30 days, we have traded approximately $30 million in notional value of both bitcoin and ether.”

Bitcoin on Monday traded at $582.79 on the Bitstamp platform, with a market capitalization of $9.1 billion, according to crypto-currency data website coinmarketcap.com.

Ether, the second-largest digital currency behind bitcoin, last changed hands at $13.92 and had a market capitalization of about $1.1 billion. (Reporting by Gertrude Chavez-Dreyfuss; Editing by Lisa Von Ahn)