(Adds comment from Finance Ministry official, opposition, paragraphs 3, 13-17)
By Deisy Buitrago and Andrew Cawthorne
CARACAS, March 24 (Reuters) - President Nicolas Maduro's government launched a new foreign exchange system on Monday, a long-awaited effort to tame Venezuela's black market for U.S. dollars and increase the flow of greenbacks to local businesses.
After authorities had missed several previously announced dates to launch Sicad 2, the central bank said the platform was ready for trading. (http://www.bcv.org.ve/c1/lonuevo.asp)
"The system's started," a Finance Ministry official, who asked not to be named, told Reuters.
The new platform adds a third exchange rate to 11-year-old currency controls that sell dollars at 6.3 bolivars for preferential goods and around 11 bolivars for other items.
Officials say Sicad 2 will help lower the price of dollars on the illegal market, where greenbacks currently fetch around 57-58 bolivars. The price has fallen from 85 a couple of weeks ago on expectations of greater dollar flows via Sicad 2.
In 2003, Maduro's predecessor, the late Hugo Chavez, set up currency controls in a socialist-style overhaul of the economy that he said would channel more wealth to workers rather than to wealthy people with bank accounts abroad.
Critics say the controls spawned corruption, curtailed business, and gave birth to the black market for dollars.
Wall Street economists and bondholders welcomed the new system as a much-needed easing of controls, though they want Maduro to go further across the economy.
Most Venezuelan bond prices were up on Monday, with the benchmark sovereign global 2027 gaining 1 percent to a bid price of 74.625.
Dollars can be offered in cash or bonds via Sicad 2 at a price above the other two official rates, but lower than the black market rate. Officials say the system will operate daily, and that businesses and individuals can take part.
Economists have speculated that the price of the dollar via Sicad 2 could vary anywhere between 20 and 50 bolivars.
Trading takes place during the morning.
"It is going to cover 7, 8 percent of real (dollar) demands, seeking equilibrium as regards the flow of foreign currency necessary for the functioning of the economy," Maduro said in a speech on Friday.
Sicad 2 essentially revives a previous system, known locally as the "permuta" or "swap" market, which Chavez shuttered in 2010 after accusing speculators of manipulating it.
Opposition politicians have long criticized the government's currency controls. Still, they are lambasting Maduro for what they call a "stealth devaluation" via the new system.
"Today will be 'black Monday'. Sicad 2 is another devaluation for our currency," Tweeted opposition leader Henrique Capriles. "Nicolas has also finished off the bolivar. Another blow to the poor."
Venezuela's annual inflation rate, currently at more than 56 percent, is the highest in the Americas. (Editing by Daniel Wallis, Paul Simao and David Gregorio)