Greek lawmakers are set to back their new unity government in a symbolic vote Wednesday, offering some comfort for Prime Minister Lucas Papademos as he races to avert bankruptcy. Growth data released Tuesday revealed the extent of the challenge facing the 64-year-old leading a unity coalition agreed last week under pressure from Greece\'s European Union and International Monetary Fund creditors. The economy shrank 5.2 percent in the third quarter, figures from the state statistics agency showed, short of an annual estimate of 5.5 percent. The Athens stock exchange also endured another miserable day, with the general index closing down 3.57 percent and the FTSEB banking index falling 9.37 percent. President Barack Obama said Tuesday the United States would stand with Greece through \"difficult times\", in a phone call to Papademos\' predecessor, George Papandreou, the White House said. In a confidence vote in parliament on Wednesday, at least 250 of the 300 lawmakers are expected to back Papademos and his new government comprising the socialist (Pasok), conservative (New Democracy) and far right (Laos) parties. But the prime minister\'s success in the task ahead is far from assured, as he races to adopt deeply unpopular reforms demanded by the EU and IMF before the release of bailout loans needed to avert bankruptcy. The coalition parties\' full support for the austerity measures is not guaranteed as they angle for early elections within a few months, while the reaction of the public to his administration remains an unknown. Polls suggest the new government has popular support, but unions and left-wing parties are mobilising against the ongoing austerity drive. The first major social challenge for Papademos comes on Thursday, at a demonstration for the annual commemoration of a 1973 student uprising that helped bring down the army dictatorship which ran Greece until 1974. Last year, the march morphed into a protest by thousands against government austerity measures, and the police are braced for trouble. Greece turns to Papademos, a former European Central Bank deputy chief, in its darkest hour, to save itself from ruin and a humiliating eurozone exit. As a priority, the debt-riddled country must unblock eight billion euros in loans due from a first EU-IMF rescue deal agreed in May 2010, which has been frozen since August. But while doing that, it must also ratify a follow-up rescue package agreed in October by the eurozone that would slash its huge debt by nearly a third and requires Greece to implement further austerity measures. There appeared to be some movement Tuesday on crucial plans agreed at a eurozone summit last month to write off 50 percent of privately owned Greek debt. A finance ministry source said talks with the banks would start \"this week\", after the Kathimerini daily reported they would begin in Frankfurt on Wednesday. EU, European Central Bank and IMF officials are due to visit Athens on Friday to assess whether conditions are ripe to unblock the funds, while Papademos will go to Brussels for talks with European officials next Monday. Hoping to delay a possible default, the Greek debt management agency managed to raise 1.3 billion euros ($1.78 billion) Tuesday in a sale of three-month treasury bills, paying rates of 4.63 percent, just an inch up from 4.61 percent paid in October. In his maiden speech to parliament on Monday at the start of the three-day confirmation procedure, Papademos said the reforms necessary to keep Greece in the eurozone would only be achieved through national unity. \"We can address the crisis faster and at a lower cost through national understanding and social cohesion,\" he said.