(Adds details from statement, background) KHARTOUM, May 20 (Reuters) - Sudan’s central bank is launching a system of foreign currency auctions as part of its flexible but managed floatation of the Sudanese pound, it said on Thursday. The new system, which would apply only to importers, comes as the official and black market rates have begun to widen slightly over the past month after being brought in line by a devaluation in February. “It is still too early to judge the results of the macroeconomic policy, including the unification of the exchange rate,” the bank said in a statement. On Thursday, a dollar fetched 420 Sudanese pounds on the black market, compared to the official rate of almost 410 Sudanese pounds. Currency traders say that part of the reason for the widening is importers resorting to the black market when banks are unable to provide sufficient foreign currency. The first auction is expected to be held next week, a senior central bank source told Reuters, adding that the policy was expected to increase supply for importers and restore stability to the exchange rate. The foreign currency bought must be used for the aim stated during the auction, a central bank circular said, and the minimum entry amount was $20,000 per bank client. Government officials said in February there would be restrictions on the import of unnecessary goods in an effort to narrow the country’s trade deficit, but specific restrictions have not been announced. Sudanese banks and exchange bureaus have bought foreign currency worth $1.2 billion since a devaluation in February, the statement said. The total amount “used to meet various client needs” was equivalent to $760 million, it said. An electronic system allowing all market participants to trade foreign currency would be implemented soon, it added. (Reporting by Khalid Abdelaziz; Writing by Nafisa Eltahir; Editing by Andrew Cawthorne and Richard Chang) Our Standards: The Thomson Reuters Trust Principles.