Greece's far-left government have proved "aggressive" in lengthy cash-for-reforms talks, the head of an influential German think tank told CNBC, adding that all of Athens' bailout supervisors must share the strain of negotiating.
"You have seen what kind of wording Greece used during the crisis to really change the mood in Europe and I think it's fair to say they have been aggressive," the president of the Ifo Institute for Economic Research, Hans Werner-Sinn, told CNBC on Wednesday.
He added: "It is easier for the Europeans if the IMF (International Monetary Fund) shares in the burden of absorbing this attitude, rather than everything being imposed on the other European countries – this is a recipe for hassle and strife."
Greece is engulfed in debt to both the European Central Bank and the IMF and needs urgent aid to save it from defaulting on a 1.6 billion euro ($1.8 billion) debt at the end of the month. However, it has fought against creditors' demands for further economic, social and political cuts and reforms.
"The IMF is skeptical about the Greek proposals as I understand. They say the Greeks promised to increase their taxes, but they have not been very good in raising taxes in the past. So it's more credible if they promise to cut wages or government employees or pensions and that is the issue about they are discussing," Sinn told CNBC.
In addition to his role at Ifo, Sinn is an adviser to the Germany economy ministry and a professor of economics and public finance at the University of Munich. He is due to retire from Ifo in March 2016.