Prime Minister Alexis Tsipras on Sunday had a phone contact with German Chancellor Angela Merkel, according to government sources.
Tsipras and Merkel expressed their common desire for constant communication throughout the course of the negotiations in order to achieve a mutually beneficial solution.
The Greek prime minister also spoke on the phone with the president of the Eurogroup Jeroen Dijsselbloem.
The president of the Council of Economic Advisors (SOE) Giorgos Chouliarakis had a phone contact with the European Commission official Declan Costello. The two officials agreed to start immediately the procedures of the Brussels Group.
A teleconference of the Brussels Group has been scheduled for Monday and a meeting will take place on Wednesday.
Earlier on Sunday, the Prime Minister met with the Government Vice President Yiannis Dragasakis, Finance Minister Yanis Varoufakis, Alternate Foreign Minister for International Economic Relations Euclid Tsakalotos and other officials.