Greece is in talks with visiting European Union and international officials about last-minute changes to its promised austerity program, which threatens to open a €3.5 billion ($5.02 billion) hole in the country's 2011 budget, a government official said Thursday.

Filling that gap is now at the center of discussions in Athens this week between Greek officials and representatives from the EU, the European Central Bank and the International Monetary Fund-called the "troika" in Greece.