The Greek government has met with its international lenders in an attempt to iron out differences over proposed cutbacks.
Inspectors from the so-called troika arrived in Athens on Monday to a frosty reception from protesters.
Ministers agreed a 13.5 billion euros austerity budget last week that foresees new cuts and fresh tax hikes.
But the delegation from the European Central Bank, the IMF and the European Commission still has objections.
Officials quoted by the Wall Street Journal said they have already rejected around two billion euros of savings, especially those relating to public sector job cuts.
The troika is reportedly concerned that the plans lack too much detail to be taken seriously.