The Taoiseach Enda Kenny has strongly criticised the Greek government for what he called "the strength of language" from Greek ministers in recent days.
He also said the Greek government had to "face up to their responsibilities".
Speaking on his arrival at a summit of EU leaders in Brussels Mr Kenny said: "There is a difference between political argument and disagreement and threats of releasing jihadists and terrorists in Europe."
Mr Kenny was referring to a threat by the leader of the junior coalition party in the Greek government, Panos Kammenos, to release "millions of economic migrants" and jihadists from detention centres into Europe if the EU did not lower its demands for austerity and reforms in Greece.
Mr Kenny told reporters: "That is not acceptable."
The Taoiseach said that tonight's meeting between the Greek prime minister Alexis Tsipras and the leaders of France and Germany, on the margins of the EU summit, would be a "difficult" one.
"But the feeling among the political leaders is that Greece and the Greek politicians have to face up to their responsibilities here. The ball is in their court.
"The [Greek] prime minister has asked for time and space and he has been given that to come forward with sustainable and workable proposals.
"Obviously Greece needs to reflect on that very quickly because time is running out."
Under a deal reached between Greece and the eurozone in Febuary, Athens must implement a detailed series of reforms in order to access €7.2 billion in bailout funds by the end of April.
However, there are indications that Greece could run out of money before then because of a sharp decline in tax revenues.
Rhetoric between Greek politicians and Berlin has escalated in recent days.
The Greek government has also criticised the ECB over its decision not to increase the amount of short term government bonds it can issue to Greek banks as a way to remain solvent in the coming months.
Frankfurt has also kept a tight limit on the amount of emergency funding Greek banks can access from the ECB.
There will be a meeting on Monday in Berlin between the German Chancellor Angela Merkel and Mr Tsipras.
