MADRID, June 18 (Reuters) - Spain"s BBVA (BBVA.MC) said on Friday said it was launching a bitcoin trading service for private banking clients in Switzerland interested in digital asset investment. The bank said the new business, launching on June 21, would include bitcoin trading and custody services, with the aim of extending it to other cryptocurrencies. It would not offer advice on these types of investments, it said. BBVA said that during a gradual roll-out it had detected a "significant desire" among investors for crypto-assets or digital assets to diversify their portfolios despite their volatility and high risk, BBVA Switzerland"s Chief Executive Alfonso Gomez said in statement. The trading service comes amid growing institutional interest in bitcoin. The largest cryptocurrency is seen by investors and some companies as a hedge against inflation as governments and central banks turn on the stimulus taps. El Salvador has become the world"s first country to adopt bitcoin as legal tender even though central banks globally have repeatedly warned that investors in the cryptocurrency must be ready to lose all their money. read more Major economies, including China and the United States, have signaled in recent weeks a tougher approach, while developing plans to develop their own central bank digital currencies. In May Goldman Sachs (GS.N) revealed details of a cryptocurrency trading group, according to a staff memo seen by Reuters. read more On Friday, BBVA said it was limiting this new cryptocurrency service to Switzerland because the country has clear regulation and widespread adoption of digital assets. "Its extension to new countries or other types of customers will depend on whether the markets meet the appropriate conditions in terms of maturity, demand and regulation," it said. BBVA is present in Switzerland through a fully owned franchise, focused on international banking services.