The sources said the central bank's Governing Council remains divided over whether to buy Italian bonds and even some of those who favor the move say Italy should do more to front-load austerity measures first. Three sources said ECB President Jean-Claude Trichet has called a teleconference of the policy-setting council for Sunday afternoon to discuss the continuing turmoil on financial markets and how to respond to Italy's latest reform pledges. "Tomorrow afternoon, the ECB will hold a conference call to discuss the general situation and possible measures that the ECB could take," one monetary source said. The decision by credit ratings agency Standard & Poor's to downgrade the United States' AAA rating to AA+ on Friday seems bound to aggravate turbulence when markets reopen on Monday. Finance ministers and central bankers of the Group of Seven industrial powers, including Trichet, are to hold a conference call on the market turmoil on Sunday, a senior European diplomatic source said. Italian and Spanish bond yields hit 14-year highs above 6 percent last week even after the ECB decided to resume buying bonds of euro zone sovereigns in difficulty, because it limited its purchases to Irish and Portuguese bonds. ECB policymakers made clear that Rome would have to accelerate fiscal and structural economic reforms before the central bank would consider buying Italian debt. Prime Minister Silvio Berlusconi announced late on Friday he would bring forward measures to balance the budget by one year to 2013, anchor a balanced budget rule in the constitution and push through welfare and labor market reforms after talks with labor unions and employers. Asked whether the announcement, made under strong pressure from European Union peers and the central bank, was enough to persuade the ECB to buy Italian bonds, once ECB source said: "I'm not sure that it's sufficient but it is going in the right direction. "They should do a bit more because the Italian program is still back-loaded and most of the measures still don't bite until after the 2013 election," the source said. Other ECB sources said that the four German, Dutch and Luxembourg members of the 23-member Governing Council who voted against re-activating the ECB's bond-buying program last Thursday remained opposed to the move in principle. "In case of such a 'deal' with the Italians, the ECB would ultimately be leaving the area of monetary policy," one source in that camp said. Another said Trichet and the majority of the ECB council seemed willing to "play a game" with the Italians, but that would depart from the central bank's proper role as responsible for monetary policy. ECB sources said it would require a further decision of the Governing Council to authorize the purchase of Italian and Spanish bonds, but this could be taken quickly by teleconference if the conditions were met. European Economic and Monetary Affairs Commissioner Olli Rehn praised the Italian moves in a first official EU reaction and said swift implementation would now be crucial. Asked in a telephone interview with Reuters whether the Italian moves were sufficient to persuade the ECB to buy Italian bonds, Rehn said he could not speak for the central bank, which is independent from political authorities. However, he said: "The commission's view is that the fiscal strategy is striking the right balance. The essential thing is rigorous implementation."