Venezuela has launched a cryptocurrency in an attempt to bypass tough economic sanctions imposed by the US government.The "Petro" is intended to bolster the country's crumbling economy, which has been suffering from hyperinflation and devaluation for years.Venezuela claims it is the world's first sovereign cryptocurrency.Critics say the move is a desperate attempt by Caracas to raise cash at a time when Venezuela lacks the ability to repay its $150bn of foreign debt.Opposition leaders said the sale constitutes an illegal issuing of debt, while the US Treasury Department warned it may violate sanctions imposed last year.The government says the currency aims to circumvent US sanctions on the economy.President Nicolas Maduro has said each token will be backed by a barrel of Venezuelan crude. The Latin American country has the world's largest proven oil reserves.A total of 100 million Petros will be sold, with an initial value set at $60, based on the price of a barrel of Venezuelan crude in mid-January.The official website published a guide to setting up a virtual wallet in which to hold the cryptocurrency, but did not provide a link for actually doing so on Tuesday.There was also no information on exchanges.Venezuela's economic crisis has largely been triggered by a slide in oil prices and production, which accounts for 96% of exports.